Release comes from Latin relaxāre — 'to loosen again' — through Old French relaissier. It is a doublet of relax: the same Latin word that arrived in English twice, by different routes.
To set free from confinement, restraint, or obligation; the act of setting something or someone free.
From Old French relaissier meaning 'to relinquish, to let go', from Latin relaxāre meaning 'to loosen again, to stretch out', from re- 'back, again' + laxāre 'to loosen', from laxus meaning 'loose, slack, wide'. The original sense was physical — loosening a grip, slackening a rope. The same root gives us relax (to loosen again), lax (loose), and lace (something threaded loosely). Release and relax are doublets: the same Latin word that entered English by two different routes. Key
Release and relax are doublets — both come from Latin relaxāre ('to loosen again'), but they entered English by different routes. Release came through Old French, which reshaped the word beyond recognition. Relax was borrowed later directly from Latin, keeping its original form. They mean almost the same thing