Old English siðe, sigði, from Proto-Germanic *segitho "sickle" (source also of Middle Low German segede, Middle Dutch sichte, Old High German segensa, German Sense), from PIE root *sek- "to cut." The sc- spelling crept in early 15c., from influence of Latin scissor "carver, cutter" and scindere "to cut." Compare French scier "saw," a false spelling from sier.
1570s, "use a scythe;" 1590s "to mow;" from scythe (n.). From 1897 as "move with the sweeping motion of a scythe." Related: Scythed; scything.