The headword is an epic noun, from o)ari/zw: LSJ entry at web address 1, and cf. omicron 2, omicron 3.
(The glossing phrase, here only, calls to mind gunaikoplhqh\s o(/milos in Aeschylus, Persians 121, used of women shouting o)a= 'woe'.)
Apart from being the title assigned to Theocritus - or ps.-Theocritus - Idyll 27, this noun is used only in Homer's Iliad, twice of the rapid exchanges in battle (13.291, 17.228: web addresses 2 and 3), once of one of the pleasures caused by the power of Aphrodite's breast-band (14.216: web address 4). It is well translated by Robert Fagles (The Iliad of Homer, 1990) as "give-and-take". See omicron 2 and omicron 3, for the etymology and semantic history of the word, and the reasons why it sometimes refers to the give-and-take of lovers.