Etymology
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conch (n.)

"large sea-shell," originally of bivalves, early 15c., from Latin concha "shellfish, mollusk," from Greek konkhē "mussel, cockle," also metaphoric of shell-like objects ("hollow of the ear; knee-cap; brain-pan; case round a seal; knob of a shield," etc.), from PIE root *konkho- (source also of Sanskrit sankha- "mussel") or else from a Pre-Greek word.

Since 18c. used of large gastropods. As a name for natives of Florida Keys (originally especially poor whites) it is attested from at least 1833, from their use of the flesh of the conch as food; the preferred pronunciation there ("kongk") preserves the classical one. Related: Conchate; conchiform; conchoidal.

The white Americans form a comparatively small proportion of the population of Key West, the remainder being Bahama negroes, Cuban refugees, and white natives of the Bahamas and their descendants, classified here under the general title of Conchs. [Circular No. 8, U.S. War Dept., May 1, 1875]
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*wel- (3)
Proto-Indo-European root meaning "to turn, revolve," with derivatives referring to curved, enclosing objects.

It forms all or part of: archivolt; circumvolve; convoluted; convolution; devolve; elytra; evolution; evolve; Helicon; helicopter; helix; helminth; lorimer; ileus; involve; revolt; revolution; revolve; valve; vault (v.1) "jump or leap over;" vault (n.1) "arched roof or ceiling;" volte-face; voluble; volume; voluminous; volute; volvox; volvulus; vulva; wale; walk; wallet; wallow; waltz; well (v.) "to spring, rise, gush;" welter; whelk; willow.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit valate "turns round," ulvam "womb, vulva;" Lithuanian valtis "twine, net," vilnis "wave," apvalus "round;" Old Church Slavonic valiti "roll, welter," vlŭna "wave;" Greek eluein "to roll round, wind, enwrap," eilein "twist, turn, squeeze; revolve, rotate," helix "spiral object;" Latin volvere "to turn, twist;" Gothic walwjan "to roll;" Old English wealwian "roll," weoloc "whelk, spiral-shelled mollusk;" Old High German walzan "to roll, waltz;" Old Irish fulumain "rolling;" Welsh olwyn "wheel."
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