It has been in general use across loads of areas of Europe - not just Celtic ones, even accounting for how widespread Celtic cultures used to be - and also since thousands of years before Celtic cultures emerged as a distinguishable group. I don't think it'd be reasonable for any one group to claim ownership of it at this point

You can't be serious. Have you never heard of a "pantheon" before?

Also, horribly ironic, since Christianity is actually a family of individual religions. Have you seriously never heard of Roman Catholicism, Methodism, Southern Baptist, Greek Othrodox, etc. ?

Also, various pagan gods often have a central group of worshipers usually referred to as "cults". Examples would be the Cult of Odin or Cult of Athena. Members of cults primarily worship their chosen deity most people in a given culture wouldn't be as selective and worship gods when appropriate, like asking Thor for a good harvest.

Granted, this doesn't exactly apply to Celtic Paganism, but I'd be surprised if a practice common to the Greeks/Romans, Norse, Egyptians, Hindus, Zoroastrians, etc. didn't also apply

It depends on the coven/group. Celtic pagans call themselves that or sometimes Celtic Wiccans or just pagans.

It's the pagan beliefs that are rooted in Irish and Welsh history specifically. Then you have different pagan beliefs that are rooted in Norse theology or Greek mythology.

My mom raised me as Wiccan. There's about as many denominations as there are in the Christian religion.

Edit: Sometimes they'll even call themselves Druids or follow Druidism.

It’s more like a Christian being asked what their religion is, and answering “Southern Baptist/First United Methodist/Lutheran/etc”. Every religion has denominations, and Celtic Pagan is an ancient denomination of paganism.

You are right about that. But I didn't talk about history and how it effectively was deragotary term, as didn't find it relevant in this context.

"Pagan" became to mean non-christian, but afaik originally it meant "person from the countryside" - lat. paganos I believe (also see: heathen - person from the heath) - so people living in vilages and such, who took longer to convert from the old faith.

Anyway, as other commenter said somewhere here, these religions usually didn't have names historically that we know of. It was simply the religion to the people. Moreover, the religion was not centralized. The various tribes, even villages could have differences and their local gods that were worshipped. So yeah, christians came up with the umbrela term and yeah, it was developed as an insult basically. But it's what we have as a name for these religions.

I didn't find it relevant as modern day pagans mostly embraced the term and I don't think it holds same negative conotations as it did in the past.

Sometimes not even enough for geographically far relatives to come for a last visit.

I have zero terror management. I am actively panicking every day, because I believe I don't get to stay dead, which is the problem.