“You won’t find the word ‘malaforms’ in the dictionary, but it most certainly ought to be there.” – explains Scott Kaiser, the Director of Company Development at the Oregon Shakespeare Festival in Ashland.
“What do I mean by a malaform? A malaform is the unintended creation of a new word by a speaker who has mangled the pronunciation of a perfectly good existing word.”
He not only coined the word, but also provides an explanation of how they are distinguished from malaprops (or malapropisms).
“[…] where a malaprop is the imperfect use of perfectly good words, a malaform is the mangling of perfectly good words into imperfect ones.”
A quasi-contemporary example is provided:
“George W. Bush: ‘They misunderestimated the compassion of our country. I think they misunderestimated the will and determination of the commander-in-chief, too.’
(He means underestimated)”
See Mr. Kaiser’s essay on the subject of malafroms in: Voice and Speech Review, Volume 5, Issue 1, 2007, Rebusing the Fartuous Word: Malaforms and Malaprops in Shakespeare