a- + torner(turn)

〜に向きを変える

verb no object Law

formally make or acknowledge a transfer of something.: 何かの譲渡を正式に行う、認める

〔法律〕〈借地人が〉(土地譲渡による新所有者を)地主と認める

with object archaic transfer (something) to someone else.: (何かを)他の誰かに譲渡する

〔英史〕臣従関係を変更する, 新しい領主に臣従を誓う

Law formally make or acknowledge a transfer of tenancy.: 借地権の譲渡を正式に行う、認める

Middle English (in the senses ‘turn, change, transform’): from Old French atorner ‘appoint, assign’, from a- (from Latin ad ‘to, at’) + torner ‘to turn’. The spelling with o rather than u or ou, as might have been expected in English, is due to the late Anglo-Norman French form attorner, adopted in legal use.