name of the cat in "Reynard the Fox" (late 15c.), hence used as a proper name for any cat, from Flemish and Dutch Tybert, Old French Tibert. Identified by Shakespeare with masc. proper name Tibalt, which is from Old French Thibauld, from Germanic *Theobald (see Theobald).
Examples from the Web for tibert
Tibert, Tybert, and Tybalt are forms of the ancient name Thibault.Shakespeare's Tragedy of Romeo and Juliet|William Shakespeare
Then Isegrim on the one side and Bruin on the other led the poor fox to the gallows, Tibert running before with the halter.
From "Tibert," "Tib," "Tibby," also was a common name for a cat.Our Cats and All About Them|Harrison Weir