partner [ME] The word partner is an alteration of parcener ‘partner, joint heir’, from Anglo-Norman French parcener, based on the Latin for partition, and thus related to the group of words at *part. The change from ‘c’ to ‘t’ was to match part. Partner for a spouse dates from the early 17th century; the term came to be commonly applied to each person of an unmarried couple sharing a home towards the end of the 20th century. Partner in crime dates from the early 19th century.