Origin and history of temerity

"full of darkness, gloomy," late 15c., from Old French tenebros "dark, gloomy" (11c., Modern French ténébreux), from Latin tenebrosus "dark," from tenebrae "darkness," which, according to de Vaan, is dissimilated from earlier *temebrai, from PIE root *temsro- "dark" (adj.), from *temos- "darkness," for which see temerity.

Related: Tenebrosity "darkness, gloom, obscurity" (early 15c.); tenebrity "quality of being dark" (1792); tenebrious "pertaining to darkness, of a dark nature" (1590s). Tenebrose "dark in color" is attested from early 15c., from Latin tenebrosus; it was used by 1670s as "morally or mentally dark."

Tenebrific "producing darkness" is by 1773; it is implied earlier in tenebrificating (1743).

In the Spectator, mention is made of a philosopher, Mr. Weems of Lathockar, who maintained that darkness was not simply the absence of light, but that certain heavenly bodies, termed by him Tenebrific Stars, emitted rays of positive darkness, which produced "NIGHT." [footnote in Thomas Bell, "Popular Opinions," Glasgow, 1818]

Tenebrer "bearer of darkness" (early 15c.) was an epithet of Satan; compare Lucifer.

Blount (1656) has tenebrion "one that will not be seen by day, a lurker, a night-thief ; also a night-spirit, a hobgoblin." Also compare tenebrescence.

Tenebrae ("darkness") is used of certain offices of the Catholic Church during Holy Week that emphasize the spiritual darkness of the season.

1909 in the figurative sense of "complete overthrow" of something; from German Götterdämmerung (18c.), literally "twilight of the gods," from genitive plural of Gott "god" (see god) + Dämmerung "dusk, twilight," from PIE root *teme- "dark" (see temerity). Used by Wagner as the title of the last opera in the Ring cycle. It translates Old Norse ragna rok "the doom or destruction of the gods, the last day, world's end." A better transliteration is Goetterdaemmerung.