protuberance (n.)

word-forming element meaning "forward, forth, toward the front" (as in proclaim, proceed); "beforehand, in advance" (prohibit, provide); "taking care of" (procure); "in place of, on behalf of" (proconsul, pronoun); from Latin pro (adv., prep.) "on behalf of, in place of, before, for, in exchange for, just as," which also was used as a first element in compounds and had a collateral form por-.

Also in some cases from cognate Greek pro "before, in front of, sooner," which also was used in Greek as a prefix (as in problem). Both the Latin and Greek words are from PIE *pro- (source also of Sanskrit pra- "before, forward, forth;" Gothic faura "before," Old English fore "before, for, on account of," fram "forward, from;" Old Irish roar "enough"), extended form of root *per- (1) "forward," hence "in front of, before, toward, near," etc.

The common modern sense of "in favor of, favoring" (pro-independence, pro-fluoridation, pro-Soviet, etc.) was not in classical Latin and is attested in English from early 19c.

*teuə-, also *teu-, Proto-Indo-European root meaning "to swell."

It forms all or part of: butter; contumely; creosote; intumescence; intumescent; protuberance; protuberant; psychosomatic; somato-; -some (3) "body, the body;" soteriology; Tartuffe; thigh; thimble; thousand; thole (n.); thumb; tumescent; tumid; tumor; truffle; tuber; tuberculosis; tumult; tyrosine.

It is the hypothetical source of/evidence for its existence is provided by: Avestan tuma "fat;" Greek tylos "callus, lump;" Latin tumere "to swell," tumidus "swollen," tumor "a swelling;" Lithuanian tukti "to become fat;" Lithuanian taukas, Old Church Slavonic tuku, Russian tuku "fat of animals;" Old Irish ton "rump."