Lease
late Middle English: from Old French lais, leis, from lesser, laissier ‘let, leave’, from Latin laxare ‘make loose’, from laxus ‘loose, lax’.
wiktionary
From Middle English lesen, from Old English lesan(“to collect, pick, select, gather”), from Proto-Germanic *lesaną(“to gather”).
From Middle English lesen, from Old English lēasian(“to lie, tell lies”), from lēas(“falsehood, lying, untruth, mistake”).
From Middle English lese, from Old English lǣs(“meadow”), from Proto-West Germanic *lāsu(“meadow”). See also leasow.
From Middle English lesen, from Old English līesan(“to loosen, release, redeem, deliver, liberate”), from Proto-Germanic *lausijaną(“to release, loosen”).
From Middle English *lesen, from Anglo-Norman *leser, Old French lesser, laisier(“to let, let go”), partly from Latin laxō(“to loose”) and partly from Old High German lāzan(“to let, let go, release”) (German lassen), cognate with Old English lǣtan(“to allow, let go, leave, rent”) whence let.
From leash.
etymonline
lease (n.)
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.)
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" (from PIE root *sleg- "be slack, be languid"). 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.
