The Collaborative International Dictionary of English v.0.48:
Wiver \Wiv"er\, Wivern \Wiv"ern\, n. [OE. wivere a serpent, OF.
wivre, guivre, F. givre, guivre, wiver, from L. vipera;
probably influenced by OHG. wipera, from the Latin. See
Viper, and cf. Weever.]
1. (Her.) A fabulous two-legged, winged creature, like a
cockatrice, but having the head of a dragon, and without
spurs. [Written also wyvern.]
The jargon of heraldry, its griffins, its mold
warps, its wiverns, and its dragons. --Sir W.
2. (Zool.) The weever.