dependant (adj.)
also dependent, late 14c.; of persons, from 1580s, from French dépendant (adjective and noun), properly present participle of dépendre "to hang down," also "to depend," from Latin dependentem (see depend).

As a noun, from early 15c., originally "action growing out of another action." As with its relative dependence, the Latin-influenced variant (in this case dependent) co-existed through 18c., but with this word the French spelling has proven more durable in English, possibly because it has been found convenient to keep both, one (dependant) for the noun, the other (dependent) for the adjective.