The name Libby is a girl's name of English origin meaning "pledged to God". Libby and is often added to lists like British Girl Names and discussed in our forums with posts like "This or That? (Girls)".
From the experts:
Through all the years when Betty, Betsy, Beth, Liz, and Lizzie were the Elizabethan nicknames of choice, the bubblier Libby was set aside, but today it may be the most modern of all—it has already made a strong comeback in England and Wales, where it ranks Number 139.
Libby Holman was a colorful torch singer in the 1920s and '30s, Libby Smith was a mysterious character on Lost, and Carly Simon wrote a song titled "Libby."