Iacobus is a Latin translation of Yaakov, the Hebrew source of the name Jacob. This explains the terms Jacobean (used to describe the reign of Britain's James I) and Jacobite (a name for supporters of that king's descendants in their attempts to regain the throne lost by James II).
James has been a popular name for many generations. While its association with two of Christ's disciples explains some of its popularity among Christians, the 20th century has celebrated a wealth of stars named James, ranging from James Cagney to James Dean. Ian Fleming's master spy James Bond has also given the name a boost over the last few decades.