It's possible the misspelling could be due to:
* Phonetic pronunciation: "Críost" is pronounced with a silent "t" at the end, so it might sound like "Croibhriste" to someone unfamiliar with the spelling.
* Regional variations: Irish Gaelic has regional dialects, and some areas might pronounce the word differently.
* Typos or autocorrect: It's easy to make a mistake when typing, especially with the similarities in letters.
If you're unsure about the context, it's best to clarify with the person who used the word or check for other clues in the surrounding text.