I have a number of languages I want to combine into a macrofamily, and one thing they have in common is nouns that ending the the pattern *-(V)nVm, e.g. *-n-om in a PIE-esque language, -unum in an Akkadian-esque language, etc. This really looks more like two morphemes smooshed together, and since *-om is a core argument case marker in the PIE-esque language, *-(V)n- is presumably something else that isn't a case marker, but that can stack with a case marker. Like what?
One idea I thought was cool was to use this *-n- to indicate that the noun is a phrase head. Semitic languages have something similar with the "construct state", which marks the possessee, i.e. the head of a possessive phrase, e.g.
*gi iki 1.SG father "I am a father"(?) gi iki -n 1.SG father EA "my father"
But my idea generalizes this to other noun phrase types, like a noun modified by an adjective or locative expression:
*es geneš -a fish canal LOC es -in geneš -a fish EA canal LOC "the fish in the canal" *ilu mulkud white pearl ilu mulkud -un white pearl EA "a white pearl"
Or a noun modified by a relative clause:
giš g -ab ua -du house 1.SG ERG see PST "I saw the house" giš -en g -ab ua -du house EA 1.SG ERG see PST "the house that I saw" ukku -a eguš -ar deb -ek saltwater LOC blue_crab PL sit 3.PL.S "there are blue crabs in the water" ukku -n -a eguš -ar deb -ek saltwater EA LOC blue_crab PL sit 3.PL.S "the water in which there are blue crabs"
I'm glossing the *-(V)n here as EA for état d’annexion "annexed state", a term used in grammars of the Shilha Berber language for a vaguely similar marking.
This begs the question of where the hell this EA morpheme evolved from, since not all of the macrofamily has it. The World Lexicon of Grammaticalization doesn't give an origin of the construct state. I considered maybe the construct state might be derived from a 3rd person possessed marking which might in turn be derived from a pronoun or a verbal person marker, but none of the languages that have this EA morpheme also have any pronouns/person markers with /n/ at all.
Also, assuming it was originally a separate word that cliticized onto the stem... why does it occur before the case ending *-om? I guess it's just so ancient it preceded even the development of case markers? Or did it metathesize into the stem, and if so, why, since *-om-Vn is not particularly hard to pronounce?