To do that I must keep up my position, and over-familiarity would be the destruction of it.'
Never presume to cultivate an over-familiarity of manner, which is always offensive; rather be reserved—even to your best friends.
c.1200, from Old French familiarite and directly from Latin familiaritatem (nominative familiaritas) "intimacy, friendship," from familiaris "friendly, intimate" (see familiar). Meaning "undue intimacy" is from late 14c. That of "close acquaintance" is from c.1600.