Nessus was a Centaur who carried Dei'anira across the river Euenos and who for his attempt to rape her on the way was shot by Heracles with a poisoned arrow. (This, much later, and via a tortuous route involving Nessus' blood being smeared on to Heracles' tunic, caused Heracles' own death.)

Nessus' name could perhaps derive from neossos, 'young bird', 'young animal', although the exact relevance of this is hard to see. Perhaps in view of his riverside abode and the fact that he carried travellers over the river we should look for an origin nao, 'to flow'. (It may be no coincidence that the German for 'wet' is nass.)