This entry on Apollon somewhat stretches the definition of “Household Gods”, since Agyieus (Ἀγυιεύς) means ‘he of the streets’. But what is meant in this case is not the roads and highways, but the streets inside city walls (Julius Pollux, Onomasticon 9.35), along rows of houses – Apollon “at the street-door”, as the LSJ dictionary has it (off-site link).
How widespread the worship of Agyieus actually was will be something to consider later, but an altar carrying his name at any rate part of the idealized, quasi-Athenian street that was represented on the stage of theaters throughout the Mediterranean. As Julius Pollux explains, “on the stage, there is the agyieús altar (‘street altar’) set up in front of the doors” (Julius Pollux, Onomasticon 4.123), that is, in front of the facades of three houses that made up the backdrop of ancient comedies.
This is why characters in comedy will swear “by this Apollon here” (mà tòn Apóllō toutoní, Aristophanes, Thesmophoriazusae 748; Menander, Dyscolus 659, Misumenus 314 and Samia 309), or even more vividly, “by this Apollon here and the doors” (Menander, quoted in Suda, s.v. Ναὶ μὰ τόν). He is even called neighbor: “O lord, king, neighbor Agyieus, […]” (…).
The idea of a divine presence on the streets is also found in the famous opening of Aratus’ Phaenomena, although he refers this back to the all-pervading cosmic god, rather than a particular deity like Apollon: “all streets are full of Zeus, all the assemblies of people, the sea and the harbors are full of him” (Aratus, Phaenomena 2–4).
2 Agyieus as name and object
Derived from the word ἀγυιά (agyiá, ‘street’), a Roman-period grammarian tells us,
- “Agyieus (Ἀγυιεύς) means τοπίτης (topítēs, ‘of a place’).
- “And obelisks set up to gods are also called so, as in Eupolis.
- “A column tapering off into a point, set up before doors, is also called Agyieus, as in Aristophanes, Thesmophoriazusae (line 489).
- “And Apollon is called both Agyieus and Agyiates (Ἀγυιάτης),
- “And the feminine is agyiâtis (ἀγυιᾶτις), as the (sacrifice) before the gates (propylaia) of Agyieus are called agyiatid services”
(Aelius Herodianus, About Paronyms, ed. Lentz, Grammatici Graeci, vol. 3.2, p. 889 ~ Epitome of Stephanus’ Ethnica, ed. Meineke, p. 22).
This information is somewhat confusedly arranged. Firstly, there is the god Apollon Agyieus, i.e. ‘of the street’ (ephódios, Stephanus, ibid.); secondly, there are conic pillars also called agyieis (pl.) set up to gods, particularly before the doors or gates of houses; thirdly, there is worship at these places, poetically called ‘agyiatid services’ (Euripides, Ion 186).
The agyieus-‘obelisk’ is the same as the conic pillar: “It was the custom to set up pillars tapering off into a point before doors, as obelisks, in honor of Apollon Agyieus, to whom they were sacred” (Scholia on Aristophanes, Wasps 875).
The conic pillar is identical to the aigyieus-altar mentioned by Julius Pollux: “Agyieus: the altar set up before the doors in the shape of a pillar” (Hesychius, Lexicon s.v. Ἀγυιεύς), and so we can refer the expression ‘agyiatid services’ to the altars themselves: “Agyiatid services, in Euripides, are the altars before the doors, which were set up for the sake of Agyieus Apollon, who is worshipped as averter of evil before the gates” (Aelius Dionysius, Attic Words s.v. ἀγυιάτιδες θεράπαιναι).
The column can also be understood as an image of the god himself, as in the scholia on Euripides: “Agyieû (voc.): propýlaie (‘he before the gate’). They used to set up Agyieus before the gates, and he/this was a column ending in a point.” Or in a sligthly different formulation: “They used to set up statues of Apollon, as averter of evil (alexíkakos) and guardian (phýlax) of the streets, before the gates; and on this account, (Apollon) is Agyieus” (Scholia on Euripides, Phoenician Women 631).
So, in sum, “Agyieus is the conic pillar (set up) before house doors, which is sacred to Apollon, and also the god himself, as in Pherecrates’ Krapataloi: ‘O lord Agyieus, bear these things in mind along with me!’” (Pausanias, Compendium of Attic Words s.v. Ἀγυιεύς).
[Apollon’s role as guardian of the streets is sometimes explained through his identity with the Sun (Helios): Scholia in Platonem + Cornutus, Scholia in Sophoclem.]
sch eq.1320a <ἐφ‘ ὅτῳ κνισῶμεν ἀγυιάς:> ἔθυον γὰρ πρὸ τῶν εὐαγγελιῶν πρὸ τῶν πυλῶν ἕκαστος. ἀγυιὰς δὲ τοὺς ἀγυιαίους θεούς. ἀντὶ τοῦ θυσίας ἐπιτελοῦμεν τοῖς θεοῖς. VEΓΘM
Demosthenes, In Midiam 51+52; Contra Macartatum 66;
Scholia on Demosthenes 21.159;162;164
Photius, Lexicon alpha 277
4 How widespread was Agyieus’ worship?
The very fact that we have such clear information about Agyieus from ancient lexica and so on suggests that his worship required explanation to those who encountered him in their readings of classical Athenian literature. (He does not appear at all in older writings.) This is also suggested by the fact that the scholiasts and grammarians often use the past tense when describing the customs surrounding him. Of course, this can sometimes reflect the perspective of a very late, even post-antique period, so we need more specific data to understand the extent of his veneration.
Harpocration’s dictionary is especially clear about the Athenian character of the custom:
But it must be noted that his perspective is that of the Roman-period Atticists, who typically contrasted the Attikoí (the inhabitants of Athens and larger Attica, especially in the 5th-4th centuries BCE) against the Héllēnes (the mainstream of Greek-speakers of their own time), and had a more limited interest in other local traditions, especially not if they had died out. In other words, Harpocration cannot be used to prove that the custom was not shared by other regions, or that it did not continue locally.
sch vesp.875a.1 vet <ὦ δέσποτ‘ ἄναξ:> περὶ τοῦ ἀγυιέως τοῦ Ἀπόλλωνος Διευχίδας οὕτως γράφει· <“ἐν δὲ τῷ †ἰατρῷ† τούτῳ διαμένει ἔτι καὶ νῦν †ἐστι ὡς† ἀγυιεὺς τῶν Δωριέων <τῶν> οἰκησάντων ἐν τῷ τόπῳ ἀνάθη- μα, καὶ οὕτως καταμηνύει, ὅτι Δωριέων ἐστὶ τὰ τῶν Ἑλλήνων. τούτοις γὰρ ἐπὶ ⟦τὰς⟧ στρατιᾶς †† φάσματος οἱ Δωριεῖς ἀπομι- μούμενοι τοὺς ἀγυιᾶς ἱστᾶσιν ἔτι καὶ νῦν τοὺς Ἀπόλλωνος.> VΓAld>
Inscriptions also show that he was worshipped in multiple regions, but they are largely from the centuries BCE:
- Among several Attic inscriptions to him, there is one to “Apollon Agyieus Prostatēríos Patrṓos Pythíos Klaríos Paiōníos” (of-the-streets, standing-before/protector, ancestral, of Pythia, of Claros, Paeonian) from as late as the 1st century CE (IG II² 4995);
- there is one from Messene “to Apollon Agyieus”, from the 3rd cent. BCE (IG V,1 1441);
- several from Pharsalos in Thessalia, from the 5th-4th cent. BCE, to “Agyiatas” in the singular (IG IX,2 241), or “the Agyiatai” in the plural (I.Thess. I 74);
- several from Asia Minor, including one to Artemis and “Phoebus Agyieus” from Halicarnassus (McCabe, Halikarnassos Inscriptions 124).
Pausanias 1.31.6, 2.19.8, 8.32.4, 8.53.1,3,6, 10.5.8
5 Latin sources
So far, I have only quoted Greek-language texts, yet this does not necessarily make them non-Roman. What i mean is that they were largely from the Roman imperial period, as it was in this time that classical Athens became enshrined as the embodiment of Greekness, and large amounts of explanatory materials had to be produced to make Attic texts comprehensible to non-Athenian readers. Many of these readers were native Latin-speakers, or learned both Greek and Latin as literary languages in addition to some local tongue.
Unsurprisingly, then, Latin sources are essentially continuous with Greek ones when it comes to Agyieus, and as with many other originally Greek subjects, a reference in a classical Latin poet meant that explanatory materials had to be made available for students of the Latin language, too.
Specifically, there is a poem by Horace in which he incidentally addresses Apollon as Agyieu (using the Greek vocative form).
Porfyrio: Levis Agyiev. Agyiae uiae[t] Graece dicuntur. arro autem: quod ex responso oraculi in uiis publicis urbis suae Athenienses statutis altaribus sacrificare Apollini instituerint, Agyieum appellauere.
Pseudacro: Carm. 4.6.28. leuis agileu. Leuis inberbis. Agiei ([leg.] agyiae) uero Atheniensi lingua uici dicuntur, quo nomine ideo Apollo uocatus est, quia ex oraculi responso in uicis publicis urbis suae statutis altaribus ei sacrificia instituerant, unde Agieus ([leg.] Agyieus) dictus. Agyieus Apollo dicitur, quia in omnibus uicis colitur; agyias enim dicunt Graeci uicos.
This story of an oracle is an explanation not found in any extant Greek source, yet it would be a mistake to call it a Roman explanation. It is likely to be derived from a Greek-language source, and even if it were not, none of its elements are Roman or dependent on Latin idiom.
Scholia in Horatium glossarum G appendicis c. III 6, 28: Agyieu ] Villanus, quia in uillis eius statuae erant Γ
De comoedia vel de fabula 1:  At uero nondum coactis in urbem Atheniensibus, cum Apollini Νομίῳ uel Ἀγυιαίῳ , id est pastorum uicorumue praesidi deo, instructis aris in honorem diuinae rei circum Atticae uicos uillas pagos et compita festiuum carmen sollemniter cantaretur, ἀπὸ τῶν κωμῶν καὶ τῆς ᾠδῆς comoedia uocitata est, ut opinor, a pagis et cantilena composito nomine, uel ἀπὸ τοῦ κωμάζειν καὶ ἄδειν, quod est comessatum ire cantantes; quod appotis sollemni die uel amatorie lasciuientibus [choris comicis] non absurdum est.
On the other hand, sometimes Greek traditions are turned to solve peculiarly Roman intellectual problems – in a peculiarly Greco-Roman fashion (be it in Latin- or Greek-language sources).
Macrobius, Saturnalia 1.9:  Sed physici eum magnis consecrant argumentis divinitatis. Nam sunt qui Ianum eundem esse atque Apollinem et Dianam dicant et in hoc uno utrumque exprimi numen adfirment.  Etenim, sicut Nigidius quoque refert, apud Graecos Apollo colitur qui Θυραῖος vocatur, eiusque aras ante fores suas celebrant, ipsum exitus et introitus demonstrantes potentem. Idem Apollo apud illos et Ἀγυιεὺς next hit nuncupatur, quasi viis praepositus urbanis; illi enim vias quae intra pomeria sunt previous hit ἀγυιὰς appellant, Dianae vero ut Triviae viarum omnium tribuunt potestatem.  Sed apud nos Ianum omnibus praeesse ianuis nomen ostendit, quod est simile Θυραίῳ. Nam et cum clavi ac virga figuratur, quasi omnium et portarum custos et rector viarum.
6 Some final miscellanea
John Lydus 2.6
sch thesm.489.1 ἀγυιεὺς οὕτω καλούμενος Ἀπόλλων τετράγωνος.
Status: under construction