Cognate to Lithuanian árklas. From Proto-Baltic *arklas, masculine counterpart of an earlier *arkla, from *árˀtla, from *artra, from Proto-Indo-European (< *h₂érh₃trom, from *h₂erh₃- (“to plow”) — whence also the verb art, q.v. —, ultimately from *h₁er- “sparse; to crumble, to fall to pieces,” with an instrumental suffix *-trom). Cognates include Old Irish arathar, Middle High German arl, Ancient Greek ἄροτρον (árotron), Latin arātrum. (A separate meaning of "land measure" comes from an earlier variant arklis, originally (13th century) the amount of land that could be plowed with one horse and one plow, later on much more than that; by the late 18th century, arkls and arklis had merged back into one word.)