late 14c., "compensation, redress," from Old French aisement "comfort, convenience; use, enjoyment," from aisier "to ease," from aise (see ease (n.)). The meaning "legal right or privilege of using something not one's own" is from early 15c.
before vowels pyr-, word-forming element form meaning "fire," from Greek pyr (genitive pyros) "fire, funeral fire," also symbolic of terrible things, rages, "rarely as an image of warmth and comfort" [Liddell & Scott], from PIE root *paewr- "fire." Pyriphlegethon, literally "fire-blazing," was one of the rivers of Hell.
early 15c., "mitigation, relief," from Medieval Latin alleviationem (nominative alleviatio), noun of action from past-participle stem of alleviare "lift up, raise," figuratively "to lighten (a burden), comfort, console," from assimilated form of Latin ad "to" (see ad-) + levis "light" in weight (from PIE root *legwh- "not heavy, having little weight").
"to the purpose, applicable, pertinent to the matter at hand," 1550s, from French relevant "depending upon," originally "helpful," from Medieval Latin relevantem (nominative relevans), from stem of Latin relevare "to lessen, lighten," hence "to help, assist; comfort, console" (see relieve). Not generally used until after 1800.
late 14c., "petition (to God or a god) for aid or comfort; invocation, prayer;" also "a summoning of evil spirits," from Old French invocacion "appeal, invocation" (12c.), from Latin invocationem (nominative invocatio), noun of action from past participle stem of invocare "to call upon, invoke, appeal to" (see invoke).
early 15c., alleviaten, "to mitigate, relieve (sorrows, suffering, etc.)," from Late Latin alleviatus, past participle of alleviare "lift up, raise," figuratively "to lighten (a burden), comfort, console," from assimilated form of Latin ad "to" (see ad-) + levis "light" in weight (from PIE root *legwh- "not heavy, having little weight"). Related: Alleviated; alleviating.
mid-14c., of persons, "disconsolate, miserable, overwhelmed with grief, deprived of comfort;" late 14c., of persons, "without companions, solitary, lonely;" also, of places, "uninhabited, abandoned," from Latin desolatus, past participle of desolare "leave alone, desert," from de- "completely" (see de-) + solare "make lonely," from solus "alone" (see sole (adj.)). Related: Desolately; desolateness.
"sacrifice of what commonly constitutes the happiness of life for the sake of duty or higher motive," 1650s; see self + sacrifice (n.). Adjective self-sacrificed attested from 1711. Related: self-sacrificing.
Self-sacrifice goes beyond self-denial in necessarily including the idea of surrender, as of comfort, inclination, time, health, while being also presumably in the line of a real duty. [Century Dictionary]