The term "etymology" means:
(the study of) the origin of a word and the historical development of its meaning.
It effectively encompasses discussion around the origin of something.
Sanity check: are there questions about origins that can not be tagged etymology? I feel the answer is no, unless what is being discussed is not a word. Though we can consider the following:
- origin of characters is covered by the glyph-origin tag
- origin of other non-word language features is probably covered by specific tags, e.g. origin of a chengyu -> chengyuhistory or similar
- origin of other non-language items is probably going to be off-topic