lease (n.) Look up lease at Dictionary.com
late 14c., "legal contract conveying property, usually for a fixed period of time and with a fixed compensation," from Anglo-French les (late 13c.), Old French lais, lez "a lease, a letting, a leaving," verbal noun from Old French laissier "to let, allow, permit; bequeath, leave" (see lease (v.)). Figuratively from 1580s, especially of life. Modern French equivalent legs is altered by erroneous derivation from Latin legatum "bequest, legacy."
lease (v.) Look up lease at Dictionary.com
late 15c., "to take a lease," from Anglo-French lesser (13c.), Old French laissier "to let, let go, let out, leave" "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). The Latin verb also is the source of Spanish laxar; Italian lasciare "leave," lassare "loosen."

Compare release (v.). Meaning "to grant the temporary possession of at a fixed rate" is from 1560s. Related: Leased; leasing. The form has been influenced by the noun, and the modern sense of "to take a lease" might be a new 19c. formation. Lessor, lessee in contract language preserve the Anglo-French vowel.