Meaning

verb expend profusely; also used with abstract nouns

adjective very generous

adjective characterized by extravagance and profusion

originFrom Middle English laves, lavas, lavage (“extravagant, wasteful, prodigal”), from lavas (“excessive abundance”), from Old French lavasse, lavache (“torrent of rain”); possibly later conflated in some senses by Middle English laven (“to pour out”), equivalent to lave + -ish. Compare Scots lawage, lavisch, lavish (“unrestrained, excessively prodigal, extravagant”). Compare also English lavy…

Etymology from Wiktionary, CC BY-SA 3.0