cousin [ME] Our word cousin is from Old French cosin, which in turn comes from Latin consobrinus ‘mother’s sister’s child’. By the time the word had entered English it could be used for the child of an aunt or uncle. It came to be used of any relative more distant than your brother or sister, and particularly in the past to a nephew or niece: ‘How now brother, where is my cosen, your son?’ (Shakespeare, Much Ado About Nothing).