From the Latin Iacobus, which was from the Greek Ιακωβος (Iakobos), which was from the Hebrew name יַעֲקֹב (Ya'aqov). In the Old Testament Jacob (later called Israel) is the son of Isaac and Rebecca and the father of the twelve founders of the twelve tribes of Israel. He was born holding his twin brother Esau's heel, and his name is explained as meaning "holder of the heel" or "supplanter", because he twice deprived his brother of his rights as the firstborn son (see Genesis 27:36). Other theories claim that it is in fact derived from a hypothetical name like יַעֲקֹבְאֵל (Ya'aqov'el) meaning "may God protect".
The English names Jacob and James derive from the same source, with James coming from Latin Iacomus, a later variant of Iacobus. Unlike English, many languages do not have separate spellings for the two names.
In England, Jacob was mainly regarded as a Jewish name during the Middle Ages, though the variant James was used among Christians. Jacob came into general use as a Christian name after the Protestant Reformation. A famous bearer was Jacob Grimm (1785-1863), the German linguist and writer who was, with his brother Wilhelm, the author of 'Grimm's Fairy Tales'.