I would think the reason for the phonetic spelling could be that the phrase is a translation of the English "kiss my ass" which translation took place in an English-speaking milieu. We always thought growing up that the phrase was American and would have heard it from American cousins rather than from neighbours.

In that context, it would be interesting to know if the verse from Monto given above can be dated.

For those who are interested, the phrase which filled the semantic position of pogue mahone in the Irish of my neighbours would have been rendered "kurdevaire mahone" phonetically in English.

And a hidden instance of phonetic spelling of a Gaelic phrase in English would be "Smashing" with the meaning '(very) good'. This is derived from "Is maith sin/Is math sin" meaning 'That is good' and probably entered the English language from Scottish Gaelic. The final 'g' is a hypercorrection where it was felt that the pronounciation smashin was recte smashin'.