What's the "een" in Halloween?
1590s, "answerable" (to another, for something), from obsolete French responsible (13c., Modern French responsable, as if from Latin *responsabilis), from Latin respons-, past participle stem of respondere "to respond" (see respond). Meaning "accountable for one's actions" is attested from 1640s; that of "reliable, trustworthy" is from 1690s. Retains the sense of "obligation" in the Latin root word. Related: Responsibly.