古英語のswanから。原語ゲルマン語*swanaz, swan, singerに由来し、PIE*swen, to sing, to make a soundが語源である。 おそらく、死ぬ直前に美しく歌うという伝説の白鳥にちなんで名付けられたのだろう。
"Do you say no worthy wife is to be found among all these crowds?" Well, let her be handsome, charming, rich and fertile; let her have ancient ancestors ranged about her halls; let her be more chaste than all the dishevelled Sabine maidens who stopped the war--a prodigy as rare upon the earth as a black swan! yet who could endure a wife that possessed all perfections? I would rather have a Venusian wench for my wife than you, O Cornelia, mother of the Gracchi, if, with all your virtues, you bring me a haughty brow, and reckon up Triumphs as part of your marriage portion. [Juvenal]