Jacob m. Hebrew יעקב from Hebrew עקב 'heel'.
The name of one of the Biblical patriarchs of the Israelites, two of the 12 apostles, a 1st C saint, a 4th C Assyrian saint, a 5th C Persian saint, a 7th C Italian saint, a 9th C Spanish saint, two 13th C kings of Aragon, a 13th C king of Majorca, two 14th C kings of Majorca, three 15th C kings of Scotland, a 15th-16th C king of Scotland, a 16th C king of Scotland, and a 16th-17th C king of Scotland. Wycliffite Bible (1395): James. Sagradas Escrituras (1569): Jacob.
The form James, which was pronounced with two syllables throughout the Middle Ages, developed in the British Isles from the Latinization Jacomus, which led in southern France to forms like Jacme.
The English diminutive Gem is witnessed in 1379 in the relational byname Gemsoñ (WRYPT1 p. 151).