Fruitcake means fruitcake, a cake with candied fruit in it, and also someone who is a little nuts. I saw a t-shirt that said, "Respect the fruitcake" and I really like that, because I do.
My grandmother on my mother's side made stollen, German fruitcake, dry as a bone, and up to its ears in chartreuse-colored bits of citron that made you think of a thin spinster aunt in a Great Plains novel, something by Willa Cather, but, when toasted, transformed into this fragrant, buxom, bitter-sweet Christmas experience. The icing pleasantly caramelized, the citron got Italian. I looked forward to it.
Now I'm candying my own pummelos. No euphemism. They're in a reducing sugar syrup in a big copper pot as I write this. It's a fruitcake thing to do, sure, but one of the joys of adulthood is knowing exactly what kind of cake you are.