familiarity (n.) Look up familiarity at Dictionary.com
c.1200, "closeness of personal association, intimacy," from Old French familiarite and directly from Latin familiaritatem (nominative familiaritas) "intimacy, friendship, close acquaintance," from familiaris "friendly, intimate" (see familiar). Meaning "undue intimacy" is from late 14c. That of "state of being habitually acquainted" is from c.1600.