Whitlock
Usually an English nickname surname for someone with white hair or a distinctive white lock.
The #2,142 most common surname in the United States (2010 Census) — about 1 in every 18,240 Americans shares it.
Etymology
Most historical surname dictionaries explain Whitlock as a nickname from Old English elements meaning "white" plus "lock" or "tress of hair." In that reading, it originally described someone with fair hair or a noticeable white lock. A few older writers also treated it as a variant or related form of Whitelock.
History
The name is documented in England in medieval and early modern records, and later spread to North America and other English-speaking countries. Some 19th-century scholars also tried to connect it with other "white-" surnames such as Whitelock or Whitehead, but the hair-based nickname explanation is the usual one. The surname remains uncommon but familiar enough to appear widely in British and American records.
Origin
Regions
Variant spellings
Fun fact
19th-century surname writers often grouped Whitlock with color-based names like Blacklock and Silverlock, which helped strengthen the old interpretation as a hair-color nickname.
From the historical record
“ledh] WHITLOCK = Whitelock, q.v. WHITLOW (Eng.) Dweller at the White HilL [O.E. hwit + hlcBw, a hill, (burial) mound] Cp. Whitelaw. WHITMAN = Whiteman, q.v. WHITMARSH (Eng.) Dweller at the White Marsh [O.E. hwit + mersc]”
— Surnames of the United Kingdom: a concise etymological dictionary (2 vols in 1)