Thank you for the information.
I didn't know about A. Beider's Encyclopedia. I'll look it up.
For what I've been able to learn, KHAMUDIS is derived from the Hebrew Khamud (plural Khamudot, or Khamudos in the Ashkenazi pronunciation). I haven't found any other explanation.
I know that "lebed" means "swan" in Russian and also that there is the town of Lebedyn in Ukraine. I guess the most likely source is the town's name.