Tenacity

The word tenacity has its origins in the Proto-Indo-European (PIE) root ten (to stretch) and Latin tenere (to hold), tenax (holding fast, gripping, firm, steadfast), and tenacitas (an act of holding fast). By the early 15th century, the word tenacity (quality of holding fast) came to English from Latin via 14th century Old French tenacité.
 
The word tenacious comes to English around 1600.
 
In brief, tenacity is the quality or state of being tenacious, of being persistent in adhering to or seeking something valued or desired. Synonyms for tenacious include dogged, insistent, persistent, persevering.
 
How is tenacity related to perseverance? These two words have very similar meanings.
 
Persevere has its origins in the PIE root segh (to have, to hold; steadfastness, toughness). The word persevere came to English in the late 14th century meaning to persist in what one has undertaken, to pursue steadily a design or course; from Latin perseverare (continue steadfastly, persist).
 
Perhaps being tenacious is about holding fast in spite of being ‘stretched’ out of your comfort zone whereas perseverance is ‘sticking’ with something in spite of difficulties.
 
PIE ten (to stretch) is the source of numerous other English words, including abstention, attend, attenuate, catatonic, contain, contend, detention, distend, entertain, extend, hypotenuse, intend, lieutenant, maintain, obtain, pretend, sustain, tenant, tend, tender, tendon, tenement, tennis, tenor, tense, tension, tent, tenderhooks, tenure, tetanus, tonic, and others. Whew!
 
PIE ten is also related to words in other languages; for example: Sanskrit tantram (loom), Persian tar (string), Lithuanian tankus (tightened), Greek teinen (to stretch), Greek tenos (sinew), Old Church Slavonic tento (cord), and Old English bynne (thin).
 
Reference: Online Etymological Dictionary, https://www.etymonline.com/
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