acquaint (v.)

early 13c., "make oneself known" (reflexive, now obsolete); early 14c., "to gain for oneself personal knowledge of," from Old French acointer "make known; make or seek 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 cognoscere "come to know" (see cognizance).

Meaning "to inform (someone of something), furnish with knowledge or information" is from 1550s. Related: Acquainted; acquainting.