That little top part (冎) is the how it was originally drawn. It's supposed to look like a bone. It's more pronounced in the earlier drawings.

The bottom part (which is the kanji for moon and month) as a radical often means something like "flesh", and is present in the kanji for body parts.

So I don't think the whole thing was intended to be the pictograph of a skellington, or at least can't say for sure.