hayyoudaoicibaDictYouDict[hay 词源字典]
hay: [OE] Etymologically, hay is ‘that which is cut down’. It comes ultimately from the prehistoric Germanic verb *khauwan, source also of English hew, which was formed from the Indo-European base *kou-, *kow-. From it was derived the noun *khaujam, which has become German hau, Dutch hooi, Swedish and Danish hä, and English hay – ‘grass cut down and dried’.

Other English descendants of Germanic *khauwan ‘cut down’ are haggle [16], which originally meant ‘hack, mutilate’ and was derived from an earlier hag ‘cut’, a borrowing from Old Norse höggva ‘cut’; and hoe [14], which comes via Old French houe from Frankish *hauwa ‘cut’.
=> haggle, hew, hoe[hay etymology, hay origin, 英语词源]
hay (n.)youdaoicibaDictYouDict
"grass mown," Old English heg (Anglian), hieg, hig (West Saxon) "grass cut or mown for fodder," from Proto-Germanic *haujam (cognates: Old Norse hey, Old Frisian ha, Middle Dutch hoy, German Heu, Gothic hawi "hay"), literally "that which is cut," or "that which can be mowed," from PIE *kau- "to hew, strike" (cognates: Old English heawan "to cut;" see hew). Slang phrase hit the hay (pre-1880) was originally "to sleep in a barn;" hay in the general figurative sense of "bedding" is from 1903; roll in the hay (n.) is from 1945.