Baby Name books/sites are rich with variations, often with their own links, that you can follow up on. For example, from website “Think Baby Names”:
**Jacob **has 52 variant forms: Cob, Cobb, Cobby, Giacamo, Giacobbe, Giacobo, Giacomo, Giacopo, Hamish, Iacopo, Iacovo, Iago, Iakob, Iakobos, Iakov, Jaap, Jack, Jaco, Jacobo, Jacobi, Jacobus, Jacoby, Jack, Jackie, Jacko, Jacky, Jacobo, Jacobus, Jacques, Jacquet, Jago, Jaime, Jake, Jakeb, Jakie, Jakob, Jakov, Jakub, James, Jamesie, Jamey, Jamie, Jamsey, Jay, Jayme, Jim, Jimmie, Seamus, Shamus, Yakov, Yakup and Yaqub.
Read more at http://www.thinkbabynames.com/meaning/1/Jacob#dRcybovaAwAydaVF.99