> The Latin word /de:mum/ ... should permanently destroy any future inklings
> to connect Sanskrit /idam/ with Latin /idem/
Unfortunately, de:mum seems to be formed entirely within Latin, on the
pattern of supre:mum, extre:mum, postre:mum. These three are purely
phonetic realisations of inherited superlatives, e.g. supre:mus < *supresmos
< *superisimos < *superism.mos. This process requires the syncopation of
second and fourth light syllable, a process internal to Latin. So de:mum
can't be taken back to PIE.
Peter