variant of quadri-.
A Long List of Affixes: Suffixes, Prefixes, and Combining FormsSuffixes -able, -ible, -ile: (form adjs) able to, fit to, worthy, capable; apt to; subject to being ~-ed -ac: one affect with -ac, -al, -ane, -ar, -ary, -ch, -ese, -ic, -ical, -id, -ile, -ine, -ish, -ory: like, of, pertaining to; characterized by -aceae: families of plants -aceous, -ous: resemblance to a substance; full of -acy, -age, -ance, -ancy, -asm, -dom, -ence, -ency, -hood, -ism, -ity, -ment, -mony, -ness, -ry, -ship, …
Origin of quadru-
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
word-forming element meaning "four, having four, consisting of four," variant of quadri-, especially before -p-, from an older form of the element, which perhaps was influenced later by tri-.
Online Etymology Dictionary, © 2010 Douglas Harper