mid-15c., "heraldic mark;" 1530s, "knowledge, act or state of knowing," abstract noun from the past-participle stem of Latin cognoscere "to get to know, recognize" (see cognizance, which is now the usual word).
cognizable
cognizance
cognizant
cognize
cognomen
cognoscence
cognoscente
cognoscenti
cog-wheel
cohabit
cohabitate