The word tarnation was coined in 1784 in New England, but its use in the Northeast was quickly superseded by that of the South. This is sort of a mutt of words. It’s a bowdlerizing alteration of the word darnation, but it’s sort of influenced by the word eternal, kind of emphasizing eternal darnation, the latter word of which is a euphemism for damnation, so this is sort of a double euphemism. The –ation part is just a suffix, but damn, through French, comes to us from Latin damnum, which meant "loss", as in loss of salvation. Through Proto-Italic dapno, this is from Proto-Indo-European dehp, meaning "to sacrifice" or still "lose". Eternity isn't quite the etymon in tarnation, only affecting its development through influence, so I'll save that for a future post. As a word, tarnation was used most frequently in the 1800s, but there's been a recent increasing period due to its whimsical usage on the Internet.
Adam Aleksic, a leading contender for valedictorian of his high school, is a 208-month-old boy with disturbing interests in etymology, vexillology, geography, and law. Adam would like to one day visit Tajikistan and just won an essay contest on linguistics!
The Etymology Nerd