Quadruple
late Middle English (as a verb): via French from Latin quadruplus, from quadru- ‘four’ + -plus as in duplus (see duple).
wiktionary
From Middle English quadruple, from Latin quadruplus. Can be analyzed as quadri- + -uple.
etymonline
quadruple (v.)
late 14c., "to make four times as much or as many," from 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). Intransitive sense of "become four times as much" is by 1776.
quadruple (adj.)
"consisting of four parts, fourfold, four times told," 1550s, from French quadruple (13c.), from Latin quadruplus "fourfold," from quadri- "four" (from PIE root *kwetwer- "four") + -plus "-fold" (see -plus). Earlier in English as a noun, "a fourfold amount," early 15c., from Latin quadruplum.
