The adjective is first attested in 1528, the verb in 1575; borrowed from Medieval Latin incarcerātus, perfect passive participle of incarcerō (“to imprison”) (see -ate (verb-forming suffix) and -ate (adjective-forming suffix)), from Latin in- (“in”) + carcer (“a prison”) + -ō (verb-forming suffix). Common participial usage of the adjective up until Early Modern English.