Well, I too would assume it's a form of Esmé. Perhaps an English feminisation?
Esmé, of course, means "esteemed" or "loved" in Old French. It's properly feminised as Esmée in French, although unfortunately a lot of parents, ignorant of how the French feminise names (or perhaps not caring), use Esmé as a female name. (Similar to
René being used for girls, really.)
Miranda