c. 1300, rehersen, "to give an account of, report, tell, narrate (a story); speak or write words;" early 14c., "repeat, reiterate;" from Anglo-French rehearser, Old French rehercier (12c.) "to go over again, repeat," literally "to rake over, turn over" (soil, ground), from re- "again" (see re-) + hercier "to drag, trail (on the ground), be dragged along the ground; rake, harrow (land); rip, tear, wound; repeat, rehearse;" from herse "a harrow" (see hearse (n.)).
The meaning "to say over again, repeat what has already been said or written" is from mid-14c. in English; the sense of "practice (a play, part, etc.) in private to prepare for a public performance" is from 1570s (transitive and intransitive). Related: Rehearsed; rehearsing.