Jack may have fallen from its Number 1 place in England, but in the US it's as popular as it was at its height in the 1920s and 1930s. A durable, cheery, everyman form of John, Jack ranks as one of the most popular <a href="https://nameberry.com/search/boys-names/j">boy names starting with J</a>. 
Jack is a derivative of John that originated in medieval England. The name went from John to Johnkin to Jankin to Jackin to Jack. The name was so common in the Middle Ages that Jack became a generic term for a man. 
 
Jack is familiar to all from earliest childhood via Jack and Jill, Jack Sprat, Jack and the Beanstalk and Little Jack Horner et al. It is still a recent favorite for novel, TV and movie characters. 
 
Jack is at the top of the charts in Ireland and Scotland, and also ranks highly in Germany, Sweden, the Netherlands, and Belgium.
 
The jaunty Scottish version is Jock.

Jack

Lochlin

Old saints' and popes' name that went to France in the 1920s with the Russian Ballets Russes; in its Russian form, Sergei, it retains an artistic, almost effete air. 

Serge

abretell's list "2015 Baby Boy" of 3 great name ideas: Jack - Serge!

2015 Baby Boy

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