The preposition at conj. in compounds, with force of ‘at, close to, to’; frequent in Old English, and retained in some words in Middle English, as at-stand(en to stand close to, ‘adstare,’ at-rech(en to reach to, get at, at-fore(n before, at-hind(en behind. In the oldest English the prefix was æt- only when it bore the stress accent (i.e. in nouns and adjectives); ot-, (oþ-, oð-,) when unaccented (in verbs and prepositions): thus, ˈætgrǽpe grasping at, apprehensive, otˈgrípan, oþˈgrípan, to grip at, oðˈberan to bear to, bring, oðˈíewan (Gothic aˈtaugjan to show). Northumbrian had sometimes æd-, od-: cf. atew v. The forms oþ, oð, seem to have arisen in an early assimilation of ot- to óþ-, óð-, from anð-, the old accented form of and- prefix, ond-, occurring in the preposition óð, the meaning of which was not far removed from that of æt-, ot-. But in later Old English the strong form æt- (Middle English at-, in southern dialect et-) was extended to all compounds, without regard to the position of the stress. Modern English has lost all these compounds, exc. that aˈtwíte survives in twit. Atone is a modern formation of a different kind.

Representing earlier Old English oþ-, oð-, unaccented form of úð- ‘away, from’ = Gothic unþa- in unþa-þliuhan to flee away, German ent- (in part), Old High German int-, in entfliehen, Old High German intfliohan, Dutch ont- in ontvlieden to flee away. This oð-, oþ-, from úð-, being phonetically levelled with óð- from anð-, and ot- the unaccented form of æt- being assimilated to the latter (see at- prefix¹), these three prefixes ran together in form, and when at a later time the accented form æt- took the place of its own weak form ot-, oþ-, oð-, it also usurped the place of oð- from anð-, and oð- from úð-, unþ-. The last of these was by far the most frequent in use: hence the most common sense of at- prefix in Middle English is ‘from, away’ = Gothic unþa-, German ent-, as in at-bear to bear away, at-flee to flee away, at-go to go away. As úð-, oþ-, had nearly the same sense as æf-, of-, these verbs in at- often take the place of corresponding verbs in of-, as Old English oð-beran, æt-beran, = of-beran to bear away, Middle English at-come = Old English of-cyman to come off, escape, etc. Several new compounds of this type arose in Middle English, and it was even irregularly extended to French words, as in atscape v., refashioned from ascape, Old French escaper. All these are now obsolete.

Assimilated form of Latin ad- to, before t, used in all modern words from Latin.