Jack

Jack is an English name that originated in the Middle Ages as a pet form of John, itself derived from the Hebrew Yohanan, meaning God is gracious. It developed through the intermediate form Jankin, a diminutive that gradually shortened to Jackin and then Jack, making it one of the most common masculine names in medieval England. The name became so widespread that it was used as a generic term for any man or boy, reflected in expressions such as lumberjack and flapjack. Related forms include John, Jan, and the feminine variant Jacqueline, while the Scottish and Irish cognate Seán shares the same Hebrew root.