The English names Jacob and James derive from the same source, with James coming from Latin Iacomus, a later variant of the Latin New Testament form 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 [1], though the variant James was used among Christians. Jacob came into general use as a Christian name after the Protestant Reformation. In America, although already moderately common, it steadily grew in popularity from the early 1970s to the end of the 1990s, becoming the top ranked name from 1999 to 2012.
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.
The Normans brought the name to England in the 11th century but it quickly died out. It was reintroduced by the German House of Hanover when they inherited the British throne in the 18th century. A famous bearer was Frederick Douglass (1818-1895), an American ex-slave who became a leading advocate of abolition.
Among Christians, this name was originally more common in Eastern Europe. It was borne in the 12th century by Saint Elizabeth of Hungary, a daughter of King Andrew II who used her wealth to help the poor. In medieval England it was occasionally used in honour of the saint, though the form Isabel (from Occitan and Spanish) was more common. It has been very popular in England since the reign of Queen Elizabeth I in the 16th century. In American name statistics (as recorded since 1880) it has never ranked lower than 30, making it the most consistently popular name for girls in the United States.
Besides Elizabeth I, this name has been borne (in various spellings) by many other European royals, including a ruling empress of Russia in the 18th century. Famous modern bearers include the British queen Elizabeth II (1926-2022) and actress Elizabeth Taylor (1932-2011).
As an English name, Caleb came into use after the Protestant Reformation. It was common among the Puritans, who introduced it to America in the 17th century.