This is the 8986th most frequent Japanese word.
沸か
"沸か" is the stem form of the verb "沸かす," which means "to boil" or "to heat (liquid)."
In this usage, "沸か" is part of "沸き立つ," which describes a lively or bubbling atmosphere.
その場の雰囲気が沸き立っていました。
The atmosphere at the venue was electrifying.
Here, "沸か" means to boil something, such as water.
お湯を沸かしてお茶を淹れます。
I boil water to make tea.
In this context, "沸か" is used metaphorically to mean excite or stir up emotions.