propinquus

Latin edit

From prop(e) (“near”) +‎ (h)inc (“hence”) +‎ -uus. Compare longinquus.

Or the ending may come from some Proto-Indo-European *-n̥kʷo- seen in Ancient Greek ἀλλοδ-απός (allod-após), ποδ-απός (pod-após) (their first parts here correspond to Latin aliud, quod) etc. See also Proto-Germanic *-ungō.

propinquus (feminine propinqua, neuter propinquum, comparative propinquior); first/second-declension adjective

(of space) near, nearby, neighboring
Synonyms: vīcīnus, contiguus, fīnitimus, proximus

Antonyms: remōtus, longinquus
(of time) near, at hand, not far off
(of appearance) resembling, similar, like, alike
(of a relationship) kindred, related
- 27 BCE – 25 BCE, Titus Livius, Ab Urbe Condita I.14:
  propinqui regis Tatii legatos Laurentium pulsant
  The relatives of the king Tatius mistreated the ambassadors of the Laurentians

Case / Gender	Masculine	Feminine	Neuter	Masculine	Feminine	Neuter
Number	Singular			Plural
Nominative	propinquus	propinqua	propinquum	propinquī	propinquae	propinqua
Genitive	propinquī	propinquae	propinquī	propinquōrum	propinquārum	propinquōrum
Dative	propinquō	propinquae	propinquō	propinquīs
Accusative	propinquum	propinquam	propinquum	propinquōs	propinquās	propinqua
Ablative	propinquō	propinquā	propinquō	propinquīs
Vocative	propinque	propinqua	propinquum	propinquī	propinquae	propinqua

Inherited:
- Old Occitan: probenc
  - → Sicilian: pruvincu (Calabrian)
- Old Galician-Portuguese: provinco
- Old Spanish: prominco
Borrowings:
- → French: propinque
- → Italian: propinquo
- → Portuguese: propínquo
- → Spanish: propincuo

Pokorny, Julius (1959) Indogermanisches etymologisches Wörterbuch [Indo-European Etymological Dictionary] (in German), volume 3, Bern, München: Francke Verlag, page 810
Walther von Wartburg (1928–2002) “prŏpĭnquus”, in Französisches Etymologisches Wörterbuch (in German), volumes 9: Placabilis–Pyxis, page 453