It forms all or part of: alchemy; chyle; chyme; confound; confuse; diffuse; diffusion; effuse; effusion; effusive; fondant; fondue; font (n.2) "complete set of characters of a particular face and size of type;" found (v.2) "to cast metal;" foundry; funnel; fuse (v.) "to melt, make liquid by heat;" fusible; fusion; futile; futility; geyser; gush; gust (n.) "sudden squall of wind;" gut; infuse; ingot; parenchyma; perfuse; perfusion; profuse; refund; refuse (v.) "reject, disregard, avoid;" refuse (n.) "waste material, trash;" suffuse; suffusion; transfuse; transfusion.
It is the hypothetical source of/evidence for its existence is provided by: Greek khein "to pour," khoane "funnel," khymos "juice;" Latin fundere (past participle fusus) "melt, cast, pour out;" Gothic giutan, Old English geotan "to pour;" Old English guttas (plural) "bowels, entrails;" Old Norse geysa "to gush;" German Gosse "gutter, drain."
early 14c., "sincerely religious, devout, pious," especially in reference to Christian practice; mid-14c., "loyal (to a lord, friend, spouse, etc.); true; honest, trustworthy," from faith + -ful. From late 14c. in reference to a tale, a report, etc., "accurate, reliable, true to the facts." The noun sense of "true believer, one who is full of faith" is from late 14c. (Church Latin used fideles in same sense). Related: Faithfully; faithfulness. Old Faithful geyser named 1870 by explorer Gen. Henry Dana Washburn, surveyor-general of the Montana Territory, in reference to the regularity of its outbursts.