Libby
Usually a nickname-turned-surname from Elizabeth or Isabella, especially through the pet forms Lib and Libbie.
The #3,360 most common surname in the United States (2010 Census) — about 1 in every 29,042 Americans shares it.
Etymology
Libby is best understood as a surname formed from a feminine pet name, especially Lib, Libbie, or a similar short form of Elizabeth or Isabel/Isabella. In medieval and early modern English records, such nickname surnames could become hereditary and pass down to later generations. Some 19th-century writers also linked it with related forms like Libbis or Libbey, but the core idea is the same: a surname from a familiar given-name diminutive.
History
The name appears in English records by the early 1500s, and later scholarship noted that it was also well represented in the United States. In America it became established both as a surname and as a familiar given name or nickname, which may have helped its continued visibility. The spelling Libby and the related Libbey are both found in historical sources.
Origin
Regions
Variant spellings
Fun fact
Older surname dictionaries explicitly connect Libby with the nickname forms Lib and Libbie, showing how a pet name could become a lasting family name.
From the historical record
“very well represented in the United States. The present nursery name is still Libby ; for Ehzabeth and Isabel are the same name, and are interchangeable in mediaeval re- WilUuo Ljbbe, du^n, 1506^ R(c.”
— A Dictionary of English and Welsh Surnames, with special American instances