>I'm curious about
>the paradigmatic difference between *pxté:r 'father' and
>*máxte:r 'mother' in IE. Where did it come from?
Do you mean the difference in accent and stem vowel? As far as I'm aware,
only Skt shows a difference in paradigm between the two words, and that's a
post-IE development.
As for the formation of the two stems, a theory I find interesting is that
the -ter affix, used for things in opposed pairs, was added to the root for
"looking after" (peH) which we find in Latin pa:sco and elsewhere. Since it
was stressed, the root appeared as zero grade: pHter. This was then
re-interpreted as p-Hter, and the new "suffix" -Hter was added elsewhere to
make the family words (ma-Hter, bhra-Hter, dhug-Hter, etc). But this theory
doesn't explain why the accent was moved back.
Peter