late 14c., from forget + -ful. A curious formation. Used in the sense "causing forgetting" from 1550s, but almost exclusively in poetry (Milton, Tennyson, etc.). An older word in this sense was Middle English forgetel, from Old English forgitel "forgetful," from a formation similar to that in Dutch vergetel. Related: Forgetfully; forgetfulness.
forgetful of her responsibilities
forgave
forge
forger
forgery
forget
forgetful
forget-me-not
forgettable
forgivable
forgive
forgiveness