Acre
Old English æcer (denoting the amount of land a yoke of oxen could plough in a day), of Germanic origin; related to Dutch akker and German Acker ‘field’, from an Indo-European root shared by Sanskrit ajra ‘field’, Latin ager, and Greek agros .
wiktionary
From Middle English acre, aker, from Old English æcer(“field where crops are grown”), from Proto-West Germanic *ak(k)r, from Proto-Germanic *akraz(“field”), from Proto-Indo-European *h₂éǵros(“field”).
Cognate with Scots acre, aker, acker(“acre, field, arable land”), North Frisian ecir(“field, a measure of land”), West Frisian eker(“field”), Dutch akker(“field”), German Acker(“field, acre”), Norwegian åker(“field”) and Swedish åker(“field”), Icelandic akur(“field”), Latin ager(“land, field, acre, countryside”), Ancient Greek ἀγρός(agrós, “field”), Sanskrit अज्र(ájra, “field, plain”).
etymonline
acre (n.)
Old English æcer "tilled field, open land," from Proto-Germanic *akraz "field, pasture" (source also of Old Norse akr, Old Saxon akkar, Old Frisian ekker, Middle Dutch acker, Dutch akker, Old High German achar, German acker, Gothic akrs "field"), from PIE root *agro- "field."
"[O]riginally 'open country, untenanted land, forest'; ... then, with advance in the agricultural state, pasture land, tilled land, an enclosed or defined piece of land" [OED]. In English at first without reference to dimension; in late Old English the amount of land a yoke of oxen could plow in a day, afterward defined by statute 13c. and later as a piece 40 poles by 4, or an equivalent shape [OED cites 5 Edw. I, 31 Edw. III, 24 Hen. VIII]. The older sense is retained in God's acre "churchyard." Adopted early in Old French and Medieval Latin, hence the Modern English spelling, which by normal development would be *aker (compare baker from Old English bæcere).
