This brings to mind "redundant", which is in a class with "disgruntled" -- I don't recall ever seeing a dundant expression.

wrong class, bob. while there certainly is a 'gruntle' (to utter a little or low grunt), there is no dundant because the L. root redundare was formed from re(d)- + undare, to surge (the re- means back).

[btw, disgruntle uses dis- as an intensifier]