acquaint (v.)youdaoicibaDictYouDict
early 13c., from Old French acointier "make known, make acquaintance of," from Vulgar Latin accognitare "to make known," from Latin accognitus "acquainted with," past participle of accognoscere "know well," from ad- "to" (see ad-) + cognitus, past participle of cogniscere "come to know," from com- "with" (see com-) + gnoscere "know" (see notice (n.)). Originally reflexive, "to make oneself known;" sense of "to gain for oneself personal knowledge of" is from early 14c. Related: Acquainted; acquainting.
quaint (adj.)youdaoicibaDictYouDict
c. 1200, cointe, "cunning, ingenious; proud," from Old French cointe "knowledgeable, well-informed; clever; arrogant, proud; elegant, gracious," from Latin cognitus "known, approved," past participle of cognoscere "get or come to know well" (see cognizance). Modern spelling is from early 14c.

Later in English, "elaborate, skillfully made" (c. 1300); "strange and clever" (mid-14c.). Sense of "old-fashioned but charming" is first attested 1795, and could describe the word itself, which had become rare after c. 1700 (though it soon recovered popularity in this secondary sense). Related: Quaintly; quaintness.