c. 1300, relēsen, "to withdraw, revoke (a decree, etc.), cancel, lift; remit," from Old French relaissier, relesser "to relinquish, quit, let go, leave behind, abandon, acquit," variant of relacher "release, relax," from Latin relaxare "loosen, stretch out" (from re- "back" (see re-) + laxare "loosen," from PIE root *sleg- "be slack, be languid"). Latin relaxare is the source also of Spanish relajar, Italian relassare, and English relax, and the uncle of relish.
Meaning "alleviate, ease" is mid-14c., as is sense of "set free from (duty, etc.); exonerate." From late 14c. as "grant remission, forgive; set free from imprisonment, military service, etc." Also "give up, relinquish, surrender." In law, c. 1400, "to grant a release of property." Of press reports, attested from 1904; of motion pictures from 1912; of music recordings from 1962. As a euphemism for "to dismiss, fire from a job" it is attested in American English since 1904. Related: Released; releasing.
early 14c., relēs, "abatement of distress; means of deliverance," from Old French relais, reles (12c.), a back-formation from relesser, relaissier "to relinquish, quit, let go, leave behind, abandon, acquit" (see release (v.)). In law, mid-14c., "transferring of property or a right to another;" late 14c. as "release from an obligation; remission of a duty, tribute, etc."
In archery, the meaning "act and manner of releasing" (a bow, etc.) is from 1871. The sense of "action of publication" is from 1907; as "a news item or official statement (to the press)" is by 1927. The meaning "action of making a film available to theaters" is from 1912, later of musical recordings, etc. The sense of "written authorization or permission for publication" is by 1965.