What does hmu mean in txt talk?

From what I gather off of Google, it is not part of the texting language...okay, here is the definition straight from Google, copied and pasted:
"Web Definitions - hmu
A metal umlaut (also known as röck döts) is an umlaut mark that is sometimes used gratuitously or decoratively over letters in the names of heavy metal bands, for example those of Mötley Crüe and Motörhead."
Does that help you at all...? It seems like an odd slang term to me... :(