I've been working on Aunt Emma for the next issue of Casefile Clues. In searching for her in various census records, I have become convinced she pronounced her first name as "Emmer." At least that's how almost every census taker spelled it, Emmar, Emmer, Emer, etc.
Think about how the first name was said. Sometime English language names were said in ways that resulted in a wide variety of spellings.