A PIE interrogative-indefinite paradigm built from the stems*kʷi- and*kʷe- (parallel to anaphoric*i-, *e-), the former on nominative and accusative cases of all genders, the latter elsewhere, with no distinction of feminine forms, mostly "human" – "non-human". A stem*kʷo-, ano-stem adjective, with its corresponding feminine*kʷeh₂-, was originally separate, but in most languages there was some conflation with the other two, as it is from this function that the relative pronoun evolves.
Dunkel speculates about*kʷe- and*kʷi- coming from*kʷ- +*e- and*í- respectively, with*kʷ- possibly being an early contraction of*kú(“where?”) to a labiovelar. For the semantic development, compare Proto-Germanic*hwarjaz, ultimately from*kʷór +*Hyós.[1]
↑2.02.1Sihler, Andrew L. (1995)New Comparative Grammar of Greek and Latin, Oxford, New York: Oxford University Press,→ISBN, pages397-398
↑3.03.1Beekes, Robert S. P. (2011)Comparative Indo-European Linguistics: An Introduction, 2nd edition, revised and corrected byMichiel de Vaan, Amsterdam, Philadelphia: John Benjamins Publishing Company, page230
↑4.04.1De Vaan, Michiel (2008) “quis, quae, quid”, inEtymological Dictionary of Latin and the other Italic Languages (Leiden Indo-European Etymological Dictionary Series; 7), Leiden, Boston: Brill,→ISBN,pages510-511
^Kloekhorst, Alwin (2008)Etymological Dictionary of the Hittite Inherited Lexicon (Leiden Indo-European Etymological Dictionary Series; 5), Leiden, Boston: Brill,→ISBN,page490
^Derksen, Rick (2015) “kai”, inEtymological Dictionary of the Baltic Inherited Lexicon (Leiden Indo-European Etymological Dictionary Series;13), Leiden, Boston: Brill,→ISBN,pages216-217
^Kent, Roland G. (1950)Old Persian: grammar, texts, lexicon, New Haven: American Oriental Society,page178
^Ernout, Alfred,Meillet, Antoine (1985) “quī, quae, quod”, inDictionnaire étymologique de la langue latine: histoire des mots (in French), 4th edition, with additions and corrections ofJacques André, Paris: Klincksieck, published2001, page556
↑9.09.1Untermann, Jürgen (2003). "Quoius undValesiosio: zum pronominalen Genitiv im Lateinischen" inLinguistica è storia: scritti in onore di Carlo De Simone (Ricerche sulle lingue di frammentaria attestazione; 2), page 180 of 179-183
↑11.011.1De Vaan, Michiel (2008) “quī, quae, quod”, inEtymological Dictionary of Latin and the other Italic Languages (Leiden Indo-European Etymological Dictionary Series; 7), Leiden, Boston: Brill,→ISBN,pages507-508
^Bakkum, G.C.L.M (2009)The Latin dialect of the Ager Faliscus: 150 years of scholarship[1],→ISBN, pages133-134