"junior military officer," 1680s, earlier more generally, "person of inferior rank" (c. 1600), noun use of adjective subaltern "having an inferior position, subordinate" (1580s), from Middle French subalterne, from Late Latin subalternus, from Latin sub "under" (see sub-) + alternus "every other (one), one after the other" (from PIE root *al- "beyond").
