From de- + caffeine + -ation.
decaffeination (uncountable)
- The removal of caffeine.
2009 September 20, Victor Lodato, “Psychic Surgery”, in New York Times[1]:While Karson and I rested under a tree, I thought of all the things I’d tried, without success, to quell my fears: extreme exercise, decaffeination, deep breathing, blue-green algae.