1610s, "to weigh more than," from Latin praeponderatus, past participle of praeponderare "outweigh, make heavier," from prae "before" (see pre-) + ponderare "to weigh," from pondus "weight," from stem of pendere "to hang, cause to hang; weigh" (from PIE root *(s)pen- "to draw, stretch, spin").
Intransitive sense is from 1620s. Meaning "to exceed in force or power" is from 1799. In 17c. English had a verb preponder "outweigh in importance," but it seems not to have survived. Related: Preponderating; preponderation.
word-forming element making adjectives from nouns, meaning "having, full of, having to do with, doing, inclined to," from Old French -ous, -eux, from Latin -osus (compare -ose (1)). In chemistry, "having a lower valence than forms expressed in -ic."
<a href="https://www.etymonline.com/word/preponderous">Etymology of preponderous by etymonline</a>
Harper, D. (n.d.). Etymology of preponderous. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/preponderous