Jack
A nickname surname from Jack, long used as a familiar form of John and also associated with James.
The #2,382 most common surname in the United States (2010 Census) — about 1 in every 20,238 Americans shares it.
Etymology
Jack began as a familiar nickname, not originally as a surname. Historical sources note two related roots: French Jacques from Latin Jacobus, which gave the name James, and later a shift in English where Jack was often used as a nickname for John as well. Because it was such a common familiar or even contemptuous label, it readily became a hereditary surname.
History
The surname is recorded by surname scholars as a nickname name that passed into regular family use. Early writers also point out how widely Jack appears in compounds and expressions such as Jackanapes and Jack-pudding, showing how common and flexible the word became in English. In some cases related surnames may reflect spelling or nickname variation rather than a direct baptismal form.
Origin
Regions
Variant spellings
Fun fact
The word Jack was so versatile in English that it could name a person, a generic fellow, or even appear in dozens of idioms and compounds.
From the historical record
“JACK 424 JACOX J”
— A Dictionary of English and Welsh Surnames (alternate scan)