late 14c., "legal contract conveying property, usually for a fixed period of time and with a fixed compensation," from Anglo-French les (late 13c.), from lesser "to let, let go," from Old French laissier "to let, allow, permit; bequeath, leave," from Latin laxare "loosen, open, make wide," from laxus "loose" (see lax). Medial -x- in Latin tends to become -ss- or -s- in French (compare cuisse from coxa). Modern French equivalent legs is altered by erroneous derivation from Latin legatum "bequest, legacy."

late 15c., "to take a lease," from Anglo-French lesser, Old French laissier "to let, leave" (see lease, n.. Related: Leased; leasing. Lessor, lessee in contract language preserves the Anglo-French form.