"extreme venturesomeness, rashness, recklessness," late 14c., from Latin temeritatem (nominative temeritas) "blind chance, accident; rashness, indiscretion, foolhardiness," from temere "by chance, at random; indiscreetly, rashly, recklessly;" probably, etymologically, "blindly," from PIE root *temsro- "dark" (adj.), source also of Sanskrit tamisra- "dark night," tamsrah "dark;" Avestan temah "darkness;" Middle Persian tar "darkness," tarig "dark;" Lithuanian tamsa "darkness," tamsus "dark;" Old Church Slavonic tima "darkness;" Old High German dinstar "dark," demar "twilight;" Old Irish temel "darkness."
The connecting notion would be "blindly, in darkness," hence "without foreseeing." Compare Latin tenebrio "dishonest person," apparently "person who operates in darkness" (see tenebrous).
of a woman, "dark in complexion, having a brownish tone to the skin and hair," 1660s, from French brunette, fem. of brunet, from Old French brunet "brownish, brown-haired, dark-complexioned," fem. diminutive of brun "brown" (12c.), of West Germanic origin, from Proto-Germanic *brunaz (from PIE root *bher- (2) "bright; brown").
As a noun, "woman with dark hair and eyes and of a dark complexion," from 1710. The metathesized form, Old French burnete, is the source of the surname Burnett. Burnete also was used of a wool-dyed cloth of superior quality, originally dark brown.
Old English dunn "dingy brown; dark-colored," perhaps from Celtic (compare Old Irish donn "dark;" Gaelic donn "dull; dark brown; dark;" Welsh dwnn "brownish"), from PIE *donnos, *dusnos "dark." As a noun, "dun color," 1560s; as "a dun horse" from late 14c. The "horse" meaning is that the figurative expression dun is in the mire "things are at a standstill or deadlocked," which occurs in both Chaucer and Shakespeare. Dun also is likely the origin of the surnames Dunn, Dunne, Donne, Dunning, etc.
"coloring matter in solution," Middle English deie, from Old English deah, deag "a color, hue, tinge," from Proto-Germanic *daugo (source also of Old Saxon dogol "secret," Old High German tougal "dark, hidden, secret," Old English deagol "secret, hidden; dark, obscure," dohs, dox "dusky, dark").
"full of darkness," late 15c., from Old French tenebros "dark, gloomy" (11c., Modern French ténébreux), from Latin tenebrosus "dark," from tenebrae "darkness," dissimilated from earlier *temebrai, from Proto-Italic *temasra- "darkness," from PIE root *temsro- "dark" (adj.), for which see temerity. Related: Tenebrosity.
1540s, "act of darkening; state of being made dark," from Latin obscurationem (nominative obscuratio) "a darkening, obscuring," noun of action from past-participle stem of obscurare "to make dark, darken, obscure," from obscurus (see obscure (adj.) ).
