where do pronouns come from and go to

[Frans Plank]

Concerning Martin's unidirectional extension Noun > Pronoun:

Pronoun > Noun may be unnatural/rare, but is probably not impossible.

A case in point is Indo-European *-pot-/*-pet-, which has been assumed to
have been a pronoun of identity ("self") and to have, among other things,
turned into a noun, referring to the representative of a social group
("master, husband, head of the household, etc.").

References:
E. Benveniste (1954): 'Problemes semantiques de la reconstruction.' Word 10
E. Benveniste (1969): Le vocabulaire des institutions indo-europeennes,
vol. 1. Paris.
F. Plank (1978): 'Exklusivierung, Reflexivierung, Identifizierung,
relationale Auszeichnung.' In: I. Rosengren (ed.) Sprache und Pragmatik.
Lund.

An oldie but goodie concerning Pronoun > Noun is:

F.R. Blake (1934): 'The origin of pronouns of the first and second person.'
American Journal of Philology 55.

Hope to read more on this on LINGTYP.

Frans.