make hay while the sun shines

"grass mown," O.E. heg (Anglian), hieg, hig (W.Saxon) "grass cut or mown for fodder," from P.Gmc. *khaujan (cf. O.N. hey, O.Fris. ha, M.Du. hoy, Ger. Heu, Goth. hawi "hay"), lit. "that which is cut," or "that which can be mowed," from PIE *kau- "to hew, strike" (cf. O.E. heawan "to cut"). Hay-fever is from 1829; earlier it was called summer catarrh. Hayseed is from 1577 in the literal sense of "grass seed shaken out of hay;" in U.S. slang sense of "comical rustic" it dates from 1851. Haymaker in the sense of "very strong blow with the fist" is from 1912, probably in imitation of the wide swinging stroke of a scythe. Slang phrase hit the hay (pre-1880) was originally "to sleep in a barn;" hay in the general fig. sense of "bedding" (e.g. roll in the hay) is from 1903.