Epic verb (first at Homer, Iliad 6.516, the scholia to which lie behind the present entry): LSJ entry at web address 1; cf. omicron 3, omicron 4.
This verb is often connected with an old word for 'wife' o)/ar ('marriage', according to Hesychius), that occurs only at Homer, Iliad 9.327, 5.486. Mader takes the two words as from the same root. Dyer (129ff) takes the noun from ou-, the Indo-European root for "breast" and the nominal ending -ar (Benveniste 3-35), but the verb as compounded from an Aeolic prefix o-'together' and ar-, probably from the same root as ei)/rw 'fasten together in rows, as in a necklace' (cf. Frisk). See Bibliography below. Dyer shows that the relationship is not etymological but rather a semantic development between two words of different origin in which the noun for a sexual partner gives its meaning as an overtone to the verb for conversations and other close encounters.
This semantic history is illustrated by the entry here in the Suda and by the noun o)/aros, a back-formation from o)ari/zw, first found at Hesiod, Theogony 205 and in the Homeric Hymns (Hymn to Aphrodite 249; Hymn 23.3), cf. Empedocles and Pindar. This noun represents a tool of Aphrodite in achieving her purposes. Mader translates it (482), "Private, intimate love talk and activity,… personal, private conversation about important matters" ("vertrauensvolles, intimes Liebesgespräch, -umgang,… persönliches und vertrauliches Gespräch, bei dem es um ernsthafte Dinge geht").
The verb, then, and its derived nouns refer to intense, private, running conversations on matters important to the partners, such as conversations between young lovers. The best-known use of the verb is in a startling simile at Homer, Iliad 22.126ff. (web address 2, where Hector tells himself that it is too late to talk with Achilles like a boy and a girl talking in this way to each other; it is the time to fight to the death. Thus the preludes to such a fight are compared to those before the sexual act.