ק�”יש יתום

Your question is about linguistics rather than halacha. Many things misnamed but we use the names anyways. In many countries the “Labor” party names suggests they are a party of blue collar workers, when in fact they are a party of left wing pseudo-intellectuals while working class voters support other parties. We refer to someone who hates Jews as an anti-Semite, even though there are many people speaking Semitic languages including the Arabs, and most people in Malta and Ethiopia (and someone accused of being an anti-Semite can not defended himself by claiming to like Arabs). That is how language is. One should note that since one says kaddish for almost a year, as opposed to a month for other relatives, the person likely to be saying kaddish in shul is usually saying it for a parent, which is probably how the term developed.

akuperma> the person likely to be saying kaddish in shul is usually saying it for a parent,

primary obligation is on the son if available, so most obligations will be on him.

The Chiyuv of Kaddish is not on a brother.

Regarding �”לוית �”מת and � י�–ום א�’לים, in truth they are both expounding upon �’מילות �–ס�”ים. And so, sure, every type of �’מילות �–ס�”ים is counted. However, we see that kindness that is done to a מת is considered a pure favor. That is likely why this was chosen to be spelled out, since ot exemplifies �’מילות �–ס�”ים.

@Kuvult also sometimes the rabbi’s husband says kaddish, especially if they self-identify as a “yusom” or somewhere else on the mourner-spectrum.

What’s really surprising is that there are other religions, like Judaism, where they keep jewish law and don’t profane “kaddish” with your reform pritzus.