Meaning

noun a long oar that is mounted at the stern of a boat and moved left and right to propel the boat forward

verb propel with sculls

noun each of a pair of short oars that are used by a single oarsman

originFrom Middle English sculle (“a type of oar”), of uncertain origin, possibly from North Germanic, from Old Norse skola (“to rinse, wash”).

Etymology from Wiktionary, CC BY-SA 3.0