The only free and comprehensive online etymological dictionary of the Spanish language
-que "and" Conjunction suffix found only in Latin.
From Proto-Italic *-kwe 'id.' From Proto-Indo-European *-kwe 'id.'
Indo-European
Italic
Venetic -kve, Faliscan -cue, Umbrian -p, Oscan -pe
Germanic
Gothic -h
Balto-Slavic
Old Church Slavonic -kъ
Hellenic
Mycenaean -qe, Doric Greek -κα (ka)
Phrygian
Phrygian -κε (ke)
Messapian
Messapian ke "and"
Indo-Iranian
Sanskrit -ca, Avestan -ca