early 15c., "lavish, extravagant," from Latin profusus "spread out, lavish, extravagant," literally "poured forth," noun use of past participle of profundere "pour forth," from pro- "forth" (see pro-) + fundere "to pour" (see found (v.2)). Meaning "bountiful" is from c. 1600. Related: Profusely; profuseness.