Just to make it clear, this doesn't only apply to imported words (although it's probably where it's more common). It works for purely Japanese words too. For example: なるはや (naruhaya) is a 4 mora abbreviation of なるべく早く (narubeku hayaku). Another one: あけおめ (akeome) is an abbreviation of 明けましておめでとうございます (akemashite omedetougozaimasu)