Well said Declan. My feeling entirely.
When Robbie and I talked at Miskin, we had a perfectly friendly and constructive conversation on the subject. He quite rightly, did not take what he was told at face value, and raised the subject here for further discussion. In doing so, it has become clear that while the most common interpretation is 'kiss O', various people have come up with other interpretations of what was sung. That in itself raises doubt as to what the word is.
In my opinion, both yourself and Robbie have taken what I said in the right spirit. Listened, and looked into it further. This is not a matter of dogma, just discussion over song lyrics.
What I find questionable about this, is why a writer of RT's undoubted talent (and no, I am not his greatest fan) would come up with such a meaningless and feeble line as
'His mad mind had trapped him with a kiss O'
when it doesn't even give a good rhyme. 'Mist O' would have been a fairly obvious word, made a bit more sense and fitted better, but there are few takers on that.
I acknowledged in my first post that asking RT would be the ideal solution.
I think we have all got it wrong, and the real words are posted here.