Libby

Libby is a short form of the forename Elizabeth. There are two main types of such shortenings: they are convenient for writing, e.g. in lists; or they are essentially spoken pet-names, and thus informal. (See Conventional abbreviations for forenames.)

Short form	Long form	Informal or written	Other short forms	Remarks
Libby	Elizabeth	Informal	Bess(y); Betty; Eliza; Lisa; Liz; Liza; Tetty	Elsie, Elspeth, Isobel and others began as alternative forms of Elizabeth, but are now often used as names in their own right. The spelling in many European languages is Elisabeth

There is a list of similar names at Conventional abbreviations for forenames, as well as the category:short names

Note that any informal form may be spelled in different ways. Notably, any spelling listed that ends in '-ie' may be written with the ending '-y', and vice versa.