סויבל

ETYMOLOGY

Beider suggests that סויבל is of "blended Slavic-German origin." The diphthong stems from a long /oː/ present in the German cognate (NHG Zobel).
[It looks as though the initial affricate of MHG/ENHG zobel was simplified to /s/ due to the influence of the the Slavic cognates.]
MHG zobel; from OHG zobel; from East Slavic (Russian) со́боль.
Cf. Polish soból; Ukrainian соболь.