Acquaintance
Middle English (in the sense ‘mutual knowledge, being acquainted’): from Old French acointance, from acointier ‘make known’ (see acquaint).
wiktionary
From Anglo-Norman aquaintaunce, aqueintance, Old French acointance(“friendship, familiarity”), from Old French acointer(“to acquaint”). Compare French accointance.
Morphologically acquaint + -ance.
etymonline
acquaintance (n.)
c. 1300, "state of being acquainted;" late 14c., "person with whom one is acquainted;" also "personal knowledge;" from Old French acointance "acquaintance, friendship, familiarity," noun of action from acointer "make known" (see acquaint). Acquaintant (17c.), would have been better in the "person known" sense but is now obsolete. Fowler regards acquaintanceship (1792) as a "needless variant."
