wrench v.

Proto-Indo-European root forming words meaning "to turn, bend."

It forms all or part of: adverse; anniversary; avert; awry; controversy; converge; converse (adj.) "exact opposite;" convert; diverge; divert; evert; extroversion; extrovert; gaiter; introrse; introvert; invert; inward; malversation; obverse; peevish; pervert; prose; raphe; reverberate; revert; rhabdomancy; rhapsody; rhombus; ribald; sinistrorse; stalwart; subvert; tergiversate; transverse; universe; verbena; verge (v.1) "tend, incline;" vermeil; vermicelli; vermicular; vermiform; vermin; versatile; verse (n.) "poetry;" version; verst; versus; vertebra; vertex; vertigo; vervain; vortex; -ward; warp; weird; worm; worry; worth (adj.) "significant, valuable, of value;" worth (v.) "to come to be;" wrangle; wrap; wrath; wreath; wrench; wrest; wrestle; wriggle; wring; wrinkle; wrist; writhe; wrong; wroth; wry.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit vartate "turns round, rolls;" Avestan varet- "to turn;" Hittite hurki- "wheel;" Greek rhatane "stirrer, ladle;" Latin vertere (frequentative versare) "to turn, turn back, be turned; convert, transform, translate; be changed," versus "turned toward or against;" Old Church Slavonic vrŭteti "to turn, roll," Russian vreteno "spindle, distaff;" Lithuanian verčiu, versti "to turn;" German werden, Old English weorðan "to become;" Old English -weard "toward," originally "turned toward," weorthan "to befall," wyrd "fate, destiny," literally "what befalls one;" Welsh gwerthyd "spindle, distaff;" Old Irish frith "against."

old style of wrench with a jaw adjustable by a screw mechanism on the handle, 1841, from monkey (n.) + wrench (n.). Monkey was used in 19c. especially by sailors, as a modifier for various types of small equipment made for specific work (monkey-block, monkey-boat, monkey-spar, etc.), and the same notion probably is behind the name of the tool. The figurative sense of "something that obstructs operations" is from the notion of one getting jammed in the gears of machinery (compare English spanner in the works).