Because it is a word, or it's easier to say, or funnier.
It's definitely not the only case. NATO comes to mind, or GOAT, NIMBY. Yesterday I heard someone say (in a tv series episode) 'fudney' for FDNY
What it 'actually' is does not matter.
It's ICE, as in: cold as
So, you now learned that human behaviour is often silly when observed without context