My 2nd great grandfather was named Ithamar, a very rare name. In researching him, I found that census records often misspelled or changed the name to Thomas or some other name. The name is special to me now, because of the effort to find this particular grandfather.
St Ithamar was a 7th-century bishop of Rochester, the first one to be Saxon-born. He was canonised after his death and given a shrine in Rochester Cathedral.