circular (n.) Look up circular at Dictionary.com
1550s, "circular figure," from circular (adj.). Meaning "a notice circulated" is from 1818.
circular (adj.) Look up circular at Dictionary.com
late 14c., from Anglo-French circuler, Old French circuler "circular" (14c., Modern French circulaire), from Latin circularis, from circulus (see circle (n.)). The metaphoric circular firing squad is attested by 1990.