An Etymological Dictionary of the German Language/Annotated/Schwan
Schwan, masculine, ‘swan,’ from the equivalent Middle High German swane, swan, masculine, Old High German swan, masculine (swana, feminine); corresponding to Dutch zwaan, Anglo-Saxon swǫn, English swan, Old Icelandic svanr, masculine, ‘swan’; Gothic *swans is by chance not recorded. Probably allied to the Sanscrit root svan, ‘to rustle, resound’ (compare Hahn, allied to Latin canere), Latin sonare (for *svonare); properly only of the singing swan?.