===Etymology

=

Others suggestions are:

for *prōprīvus, from prīvus or ultimately from this root.
for *prōpatrius, from prō- + pater, meaning "from one's forefathers", taking Antički Grčki προπάτωρ (propátōr, “forefather”) as comparison.

prōprius (feminine prōpria, neuter prōprium); first/second-declension adjective

Case / Gender	Masculine	Feminine	Neuter	Masculine	Feminine	Neuter
Number	Singular			Plural
Nominative	prōprius	prōpria	prōprium	prōpriī	prōpriae	prōpria
Genitive	prōpriī	prōpriae	prōpriī	prōpriōrum	prōpriārum	prōpriōrum
Dative	prōpriō	prōpriae	prōpriō	prōpriīs
Accusative	prōprium	prōpriam	prōprium	prōpriōs	prōpriās	prōpria
Ablative	prōpriō	prōpriā	prōpriō	prōpriīs
Vocative	prōprie	prōpria	prōprium	prōpriī	prōpriae	prōpria

“proprius”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
“proprius”, in Charlton T. Lewis (1891) An Elementary Latin Dictionary, New York: Harper & Brothers
proprius in Charles du Fresne du Cange’s Glossarium Mediæ et Infimæ Latinitatis (augmented edition, 1883–1887)
proprius in Gaffiot, Félix (1934) Dictionnaire Illustré Latin-Français, Hachette
Carl Meissner; Henry William Auden (1894) Latin Phrase-Book‎^[1], London: Macmillan and Co.
- the proper term; a word used strictly: vocabulum proprium
- something is a characteristic of a man: aliquid est proprium alicuius
Pokorny, Julius (1959) Indogermanisches etymologisches Wörterbuch [Indo-European Etymological Dictionary] (in German), volume III, Bern, München: Francke Verlag, page 829