Old name for Irish or sometimes Scottish Gaelic (4)

I believe the answer is:

erse

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'scottish gaelic' is the definition.
(I've seen this in another clue)

I can't explain the rest of the clue.

(Other definitions for erse that I've seen before include "Old Scots or Irish Gaelic" , "Old Celtic language" , "Old language spoken by strange seer" , "Celtic tongue" , "Possibly the language" .)

I've seen this clue in The Times.

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