Unleash is from un- ('reverse') + leash, from Old French laisse ('thong, leash'), from laissier ('to let go, leave'), from Latin laxare ('to loosen'), from laxus ('loose'). Important recorded forms include un- (Old English), laisse (Old French), and laxare (Latin). Morphologically, the un- element marks negation, reversal, removal, or deprivation, while the base supplies the action, quality, or state being denied or undone. The modern sense is largely compositional, with the historical elements narrowing into a stable English lexical item. In current use it covers to release from restraint and allow free action. The wider family includes derived forms such as unleashed and unleashing and related words such as leash and leashed.