"student who pronounces the oration at commencement exercises of his or her class," 1832, American English, from valedictory + -ian. As an adjective from 1834.
Entries linking to valedictorian
valedictory adj.
1650s, "pertaining or relating to leave-taking," from Latin valedictum (past participle of valedicere; see valediction) + -ory. As a noun meaning "valedictory address" from 1779.
-ian
variant of suffix -an (q.v.), with connective -i-. From Latin -ianus, in which the -i- originally was from the stem of the word being attached but later came to be felt as connective. In Middle English frequently it was -ien, via French.