I recently had a conversation with someone who repeatedly used "intertwound" for the past participle of intertwine. If you Google intertwound, you only get about 160 hits. Admittedly, trying to figure out why a small (160 hits out of the whole internet? Maybe "infinitesimal" is a better word.) number of people do something out of the ordinary isn't necessarily interesting or fruitful. However, these hits all seem to be unreflecting attempts at forming the past participle of intertwine, and damnit, I'm intrigued.
At first I thought this was a natural enough reanalysis to make, thinking that twine formed its participle by changing the vowel from /ay/ to /aw/. BUT! As far as I can tell, all verbs which form their participle by changing /ay/ to /aw/ have the coda /aynd/ (wind, find, bind, grind). Twine ends in /ayn/.
So how did anyone come to reanalyze twine. There are a few possibilities. First, perhaps the /ay/ → /aw/ rule generalized to twine despite its not exactly having the right phonological shape. Second, it might be the case that some people have misanalysed this structure:
for this structure
That is, they've reanalyzed the final /d/ in intertwined as actually being part of the stem. This way, the stem actually does have the /aynd/ coda, making it natural to extend the /ay/ → /aw/ rule to it.
A third possibility, and the one that I think is closer to being the correct one, is that some people have reanalyzed the structure of intertwined as