It seems that all the words in Gaelic for "God" has latin roots. Do we know of any word for a higher power in Gaelic that may have originated on the Island? Thanks

Dia has no Latin roots.
It has not originated on the island either. It has Indo-European roots.

Tiarna 'Lord' (old spelling 'tighearna') wasn't borrowed from Latin either.
What Gaelic words for "God" have Latin roots?

Ah, okay, my bad. I was hoping for a word for God that isn't borrowed from mainland Europe at some point

But the word for "God" in Irish isn't (and wasn't) borrowed from mainland Europe at any point.

Irish is an Indo-European language. The word for "God" in Irish developed naturally from the word of the same meaning used in this earlier Language stage. "Borrow" implies it was taken from another language entirely at a time when Irish already existed as a distinct language from the one donating the word.