late Middle English (denoting a dependency): from Old French, literally 'hanging down from', present participle of dependre (see depend)
Until recently the only correct spelling of the noun in British English was dependant, as in a single man with no dependants. However, the variant dependent is now standard, and indeed it is now as common as dependant in the Oxford English Corpus. In US English dependent is the standard form for the noun. The adjective is spelled -ent, not -ant, as in we are dependent on his goodwill.