Old English sciftan, scyftan "arrange, place, order," also "divide, partition; distribute, allot, share," from Proto-Germanic *skiftan (source also of Old Norse skipta "to divide, change, separate," Old Frisian skifta "to decide, determine, test," Dutch schiften "to divide, turn," German schichten "to classify," Schicht "shift"). This is said to be related to the source of Old English sceadan "divide, separate," (see shed (v.)).
c. 1200 as "to dispose; make ready; set in order, control," also intransitive, "take care of oneself." From c. 1300 as "to go, move, depart; move (someone or something), transport." Sense of "to alter, to change" appeared mid-13c. (compare shiftless). Meaning "change the gear setting of an engine" is from 1910; to shift gears in the figurative sense is from 1961. Related: Shifted; shifting.