The great psychologist Sigmund Freud would have been extremely satisfied with the origin of the word felicity, if he ever found out. This word for "happiness" can actually be traced all the way back to the Proto-Indo-European word dhe, "to suck, suckle, produce or yield". You can clearly see the... maternal origins of the word, which may be etymological proof of the Oedipus Complex. In any case, dhe lead to Latin (as many of our words seem to), and the word Felix, which like Felicity is a rather lucky name (its definition is "luck", though it doubled as "fertile" in the early times). This gave way to felicitas, or "lucky", which hung around a bit until it got picked up by the French, who used the word felicite, meaning "happy", since those who are lucky are normally happy. It took only a small hop over the Channel to become felicity, but that isn't nearly the most fascinating part of this serendipitous word. The best part is how this reflects on the human psyche, how someone somewhere equated true luck to being able to suckle milk as a baby. This is how etymology happens.
Adam Aleksic, a freshman studying linguistics at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in words, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
The Etymology Nerd