"to soften," usually figuratively, of pain, anger, passion, grief, etc., c. 1300, from Anglo-French assuager, Old French assoagier "soften, moderate, alleviate, calm, soothe, pacify," from Vulgar Latin *adsuaviare, from Latin ad "to" (see ad-) + suavis "sweet, agreeable," from PIE root *swād- "sweet, pleasant" (see sweet (adj.)). For sound development in French, compare deluge from Latin diluvium, abridge from abbreviare. Related: Assuaged; assuaging.