skank · noun, adjective1
Unknown. Perhaps from skag (“unattractive woman”), but the origins of skag are unknown. Compare scold (“troublesome woman”), skeevy (“disgusting”). Attested from the 1960s.
skank · noun, verb2
Originally Jamaican, attested from the twentieth century, but earliest source is uncertain. The verb sense be dishonest is evidently older. Perhaps originally onomatopoeic. The dance senses may come from a resemblance to motorcyclists weaving between larger vehicles. Compare skanker.
skank · noun, verb3
Slang word used in Northern England. Unknown. Perhaps from etymology 2, above; attested in West Indian and UK black slang from the twentieth century.
Etymology from Wiktionary, CC BY-SA 4.0.