Middle English shef, from Old English sceaf (plural sceafas) "large bundle into which grain is bound after reaping," from Proto-Germanic *skauf- (source also of Old Saxon scof, Middle Dutch scoof, Dutch schoof, Old High German scoub "sheaf, bundle," German Schaub "sheaf;" Old Norse skauf "fox's tail;" Gothic skuft "hair on the head," German Schopf "tuft"), from PIE root *(s)keup- "cluster, tuft, hair of the head."
Extended to bundles or collections of things other than grain by c. 1300. Also used for "a handful or quiver-ful of arrows" (late 14c.), sometimes specifically as "two dozen arrows."