\DOO-sid-lee, adverb:

Devilishly; damnably.

When I went in I had seen that there was a deucedly pretty girl sitting in that particular seat, so I had taken the next one.
— P. G. Wodehouse, Man With Two Left Feet and Other Stories

It’s most important. You will put me in a deucedly awkward position if you don’t.
— C. S. Lewis, The Magician’s Nephew

Deucedly is related to the word deuce which refers to the face of a die with one dot, as in “to roll deuces.” It comes from the Latin word for two, duos. In the mid-1600s, it became associated with bad luck, probably because it was the lowest score you could get when playing dice.