It could be ermine - we tend to use fur as trimming but in heraldry a fur is used in the same way as a colour (like red/gules) or a metal (like or/gold). the coat of arms of Brittany e.g. is simply ermine. Of the other furs in common use in heraldry, vair, ermines and erminois all have the wrong number of letters, but there is potent (which I think qualifies as a fur).
Another possibility, however, is tabard. All of the kings, heralds and poursuivants of arms wear richly embroidered tabards.