1680s, "to melt, make liquid by heat" (transitive), back-formation from fusion. Intransitive sense, "to become liquid," attested from 1800. Figurative sense of "blend different things, blend or unite as if by melting together" is recorded by 1817. Intransitive figurative sense "become intermingled or blended" is by 1873. Related: Fused; fusing.
"combustible cord or tube for lighting an explosive device," also fuze, 1640s, from Italian fuso, literally "spindle" (the ignition device so called for its shape, because the originals were long, thin tubes filled with gunpowder), from Latin fusus "a spindle," which is of uncertain origin. Influenced by French cognate fusée "spindleful of hemp fiber," and obsolete English fusee "musket fired by a fuse," which is from French. Meaning "device that breaks an electrical circuit" is first recorded 1884, so named for its shape, but erroneously attributed to fuse (v.) because it melts.
1909, from French fuselage, from fuselé "spindle-shaped," from Old French *fus "a spindle," from Latin fusus "a spindle" (see fuse (n.)). So called from its shape.
Proto-Indo-European root meaning "to pour, pour a libation."
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."
also burnout, "drug user," by 1972, slang, from the verbal phrase, which is attested from 1590s in the sense "burn until fuel is exhausted;" see burn (v.) + out (adv.). The immediate source is perhaps the use of the phrase in reference to electrical circuits, "fuse or cease to function from overload" (1931). Also compare burnt out "extinct after entire consumption of fuel" (1837). The meaning "mental exhaustion from continuous effort" is from 1975.