Tibby

Tibby is an English pet form of Isabel or Isabella, which itself descends through Old Provençal and Medieval Latin from the Hebrew name Elisheba, meaning something along the lines of my God is an oath or my God is abundance. The nickname arose through the intermediate short form Ibb, with the initial consonant shift from I to T being a common feature of medieval English hypocoristic formation, similar to the process that produced Tib and Tibbie. It was most prevalent in Scotland and northern England, where Tibbie in particular remained in use well into the modern era. Related forms include Tibbie, Ibb, Ibby, and the source names Isabel and Isabella.