Meaning

noun a person without employment who makes money by various dubious schemes; goes about smartly dressed and having a good time

originUnknown. Perhaps from spiff, spiffy. Spiv was the nickname of Henry Bagster, a Londoner arrested a number of times in 1904-6 for activities as described below, and may have been the archetype. Also possibly from Romani spiv (“sparrow”), as active and opportunistic.

Etymology from Wiktionary, CC BY-SA 3.0