Does knowing a word for an emotion cause a person to feel the emotion more frequently? I am aware of the Frequency Illusion which makes it more likely for us to notice a new word if we just heard about it recently, but I was wondering if this is true for emotions as well.

Logically, I assume it would be yes because you are more aware about your emotions and hence more likely to notice that you are experiencing the emotion. Have there been any conclusive studies done on this subject?

I don't know much about linguistics but if, say, a certain isolated tribe has not come up with a word for "happiness", would they ever feel happiness in the same way that we do, or feel it less frequently?
The answer would be no. To go along with the comments babies feel emotions however do not know words. As they grow adults help them organize their emotions for example a baby cries with frustration and anger because they may be hungry as you get older you have learned how to deal with that experience. As it is impossible to feel any emotion without having a thought first, emotions stem from what we are thinking which would be mostly concepts we don't think in random words. Therefore if we like to be happy we will think about things or do things that make us such. We are made to feel a wide range of emotions and they come and go. Knowing a word is not going to help someone know happiness better. Learning to control thoughts would be much more helpful. Just as a baby feels all emotions it does not yet understand them. What good would a huge vocabulary be if we could not put together concepts.