Etymology
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tenacious (adj.)
c. 1600, from Latin stem of tenacity + -ous. Related: Tenaciously; tenaciousness.
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pertinacity (n.)

"resolute or unyielding adherence," c. 1500, from French pertinacité (early 15c.), from Old French pertinace "obstinate, stubborn," from Latin pertinacem (nominative pertinax) "very firm, tenacious, steadfast, persevering," from per "very" (see per) + tenax (see tenacious). It drove out earlier pertinacy (late 14c.), which was especially "persevering in disbelief."

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*ten- 
Proto-Indo-European root meaning "to stretch," with derivatives meaning "something stretched, a string; thin."

It forms all or part of: abstain; abstention; abstinence; abstinent; atelectasis; attend; attenuate; attenuation; baritone; catatonia; catatonic; contain; contend; continue; detain; detente; detention; diatonic; distend; entertain; extend; extenuate; hypotenuse; hypotonia; intend; intone (v.1) "to sing, chant;" isotonic; lieutenant; locum-tenens; maintain; monotony; neoteny; obtain; ostensible; peritoneum; pertain; pertinacious; portend; pretend; rein; retain; retinue; sitar; subtend; sustain; tantra; telangiectasia; temple (n.1) "building for worship;" temple (n.2) "flattened area on either side of the forehead;" temporal; tenable; tenacious; tenacity; tenant; tend (v.1) "to incline, to move in a certain direction;" tendency; tender (adj.) "soft, easily injured;" tender (v.) "to offer formally;" tendon; tendril; tenement; tenesmus; tenet; tennis; tenon; tenor; tense (adj.) "stretched tight;" tensile; tension; tensor; tent (n.) "portable shelter;" tenterhooks; tenuous; tenure; tetanus; thin; tone; tonic.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit tantram "loom," tanoti "stretches, lasts," tanuh "thin," literally "stretched out;" Persian tar "string;" Lithuanian tankus "compact," i.e. "tightened;" Greek teinein "to stretch," tasis "a stretching, tension," tenos "sinew," tetanos "stiff, rigid," tonos "string," hence "sound, pitch;" Latin tenere "to hold, grasp, keep, have possession, maintain," tendere "to stretch," tenuis "thin, rare, fine;" Old Church Slavonic tento "cord;" Old English þynne "thin."
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glutinous (adj.)
"viscous, sticky, of the nature of glue," early 15c., from Latin glutinosus "gluey, viscous, tenacious," from gluten (genitive glutinis) "glue" (see glue (n.)). Glutinosity is from c. 1400. Related: Glutinousness.
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pertinacious (adj.)

"unyielding, persistent, resolute" (in holding to a purpose, opinion, course of action, etc.), 1620s, from pertinacy "stubbornness" (late 14c.), from Latin pertinacia, from pertinax "very firm, tenacious" (see pertinacity) + -ous. Related: Pertinaciously.

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cement (n.)

kind of mortar or other substance that hardens as it dries, used to bind, c. 1300, from Old French ciment "cement, mortar, pitch," from Latin cæmenta "stone chips used for making mortar" (singular caementum), from caedere "to cut down, chop, beat, hew, fell, slay" (from PIE root *kae-id- "to strike"). The sense evolution from "small broken stones" to "powdered stones used in construction" took place before the word reached English. Cement-mixer is from 1875.

The term properly includes papier maché, gums, glues, mucilages, limes, mortars, and a great number of compounds of such nature as to admit of their assuming, under certain conditions, sticky, tenacious, or stone-like consistency. [Century Dictionary]
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pitch (n.2)

"thick, tenacious, resinous substance obtained from tar or turpentine, wood tar," late 12c., pich, piche, from Old English pic "pitch," from a Germanic borrowing (compare Old Saxon and Old Frisian pik, Middle Dutch pik, Dutch pek, Old High German pek, German Pech, Old Norse bik) of Latin pix (genitive picis) "pitch" (source of Old French poiz), from PIE root *pik- "pitch" (source also of Greek pissa (Attic pitta), Lithuanian pikis, Old Church Slavonic piklu "pitch," Russian peklo "scorching heat, hell").

The English word was improperly applied to sap from pine bark from late 14c. As a type of blackness from c. 1300. Pitch-black "as black as pitch" is attested from 1590s; pitch-dark "as dark as pitch, very dark" from 1680s.

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lutose (adj.)

"muddy, covered with clay," from Latin lutosus, from lutum "mud, dirt, mire, clay," from Proto-Italic *luto-, *lustro-, from PIE *l(h)u-to- "dirt," *l(h)u-(s)tro- "dirty place," from root *leu- "dirt; make dirty" (cognates: Greek lythron "gore, clotted blood," lyma "dirty water; moral filth, disgrace," lymax "rubbish, refuse," lyme "maltreatment, damage;" Latin lues "filth;" Old Irish loth "mud, dirt;" Welsh lludedic "muddy, slimy; Albanian lum "slime, mud;" Lithuanian liūtynas "loam pit").

Hence also English lute (n.) as a type of tenacious clay or cement used to stop holes, seal joints, etc. (c. 1400), from Old French lut or Medieval Latin lutum, from the Latin noun. Lute also was a verb in English.

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tough (adj.)
Old English toh "strong and firm in texture, tenacious, sticky," from Proto-Germanic *tanhu- (source also of Middle Low German tege, Middle Dutch taey, Dutch taai, Old High German zach, German zäh), which Watkins suggests is from PIE *denk- "to bite," from the notion of "holding fast." See rough for spelling change.

From c. 1200 as "strong, powerful;" c. 1300 as "not tender or fragile;" early 14c. as "difficult to chew," also "hard to endure." Figurative sense of "steadfast" is mid-14c.; that of "hard to do, trying, laborious" is from 1610s. Verb tough it "endure the experience" is first recorded 1830, American English. Tough guy attested from 1901. Tough-minded first recorded 1907 in William James. Tough luck first recorded 1912; tough shit, dismissive retort to a complaint, is from 1946.
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