www.alphadictionary.com

Not much etymological history here. In fact, its history is rather obscure, you might even claim dark. We do know if comes to us from Latin via French. I wonder if the Latin root produced any other fruit.

As to direct fruit, I find only the RC church tenebrae for masses sung during holy week.

It is, however, related to a previously treated word: temerity. The guts to take a flying leap into the dark.

Thanks Slava. I can always count on you to enlighten me with interesting and little known facts.