General Discussion

Latin because the old Irish priests wrote in Gaelic Latin.
(Sometimes they had to do it in secret and the writing was on tiny pieces of paper
and teeny tiny writing.)

Also paper and ink were expensive and they didn't want to waste it.

And yes old records in the US in English are impossible at times.
Get out the magnifying glass and that still doesn't help.

The employees at Ellis Island, etc.
Census workers yes.
Actually any old document.
Don't know what they were thinking as they were writing.

Also with immigrants, I don't think the census takers understood them half the time
and just wrote whatever they thought they heard.

My Irish grandparents spoke with a very heavy Irish brogue, the family could understand them
we listened to them all the time. But other Americans couldn't easily understand them.

My grandfather was a school teacher in Ireland so was able to speak more clearly and a bit
less of an accent, and I am lucky his handwringing was perfect and very legible.
His writing was easy to read in all documents.

Many immigrants to the US were not literate, so had to have other people write down things for them.
And stuff got lost in the translation.