[1680–90; plump1 + -en1]This word is first recorded in the period 1680–90. Other words that entered Englishat around the same time include: bull's-eye, commercial, gangway, picket, reservoir-en is a suffix formerly used to form transitive and intransitive verbs from adjectives(fasten; harden; sweeten), or from nouns (heighten; lengthen; strengthen)