Pretentious
mid 19th century: from French prétentieux, from prétention (see pretension1).
wiktionary
From French prétentieux, from prétention, from Latin praetēnsus(“false or hypocritical profession”), past participle of praetendō.
Note that pretentious is spelled with a ‘t’, unlike related pretense, pretension. This is due to the French spelling: *-sious does not occur as an English suffix, though -sion and -tion both do.
etymonline
pretentious (adj.)
"characterized by or full of claims to greater excellence or importance than the truth merits," 1836, from French prétentieux (17c.), from prétention "pretension," from Medieval Latin pretentionem (nominative pretentio) "pretension," noun of action from past-participle stem of Latin praetendere (see pretend (v.)). Related: Pretentiously; pretentiousness.