quadruple (v.)

late 14c., from Middle French quadrupler, from Late Latin quadruplare "make fourfold, multiply by four," from Latin quadruplus (adj.) "quadruple, fourfold," from quadri- "four" (from PIE root *kwetwer- "four") + -plus "-fold" (see -plus).

1550s, from Middle French quadruple (13c.), from Latin quadruplus "fourfold," from quadri- "four" (from PIE root *kwetwer- "four") + -plus "-fold" (see -plus).