If you have guessed that temerarious may be related to the somewhat more common word temerity, you are correct. Temerarious was borrowed into English in the early 16th century from Latin temerarius, which in turn derives from Latin temere, meaning "blindly" or "recklessly." Temerity, which arrived in English over a century earlier, also derives from temere; another descendant is the rare word intemerate,meaning "pure" or "undefiled." Temere itself is akin to Old High German demar, Latin tenebrae, and Sanskrit tamas, all of which have associations with darkness.