bridesmaid (n.)

"young girl or unmarried woman who attends on a bride at her wedding," 1550s, bridemaid, from bride + maid. The -s- is unetymological but began to appear by 1794 and the form with it predominated by the end of the 19c. Brideman is attested from 1610s as "bridegroom;" bridesman is from 1808 as "male attendant on a bridegroom at his wedding."