Immortal
late Middle English: from Latin immortalis, from in- ‘not’ + mortalis (see mortal).
wiktionary
From Latin immortālis, from prefix im-(“not”) (from in-) + mortālis(“mortal”) (from mors(“death”), combining form mort- + adjectival suffix -alis). Displaced native undeadly, from Old English undēadlīċ.
etymonline
immortal (adj.)
late 14c., "deathless," from Latin immortalis "deathless, undying" (of gods), "imperishable, endless" (of fame, love, work, etc.), from assimilated form of in- "not, opposite of" (see in- (1)) + mortalis "mortal" (from PIE root *mer- "to rub away, harm," also "to die" and forming words referring to death and to beings subject to death). In reference to fame, literature, etc., "unceasing, destined to endure forever, never to be forgotten, lasting a long time," attested from early 15c. (also in classical Latin). As a noun, "an immortal being," from 1680s.
