a combination of -ate 1 and -ory 1 or -ory 2 , used infrequently as an independent suffix with the same senses as -ory 1 and -ory 2 : affirmatory; observatory.
[ -atorius, -a, -um, orig. the termination of adjectives formed with -torius (see -TORY 1 , TORY 2 ) and verbs whose stems ended in -a-; reanalyzed in English in the same way as -ATOR ]