
It's a hymn: the first line 'gyts fel llew oedd gan Iesu' means 'Jesus had guts like a lion', and the chorus is 'Bendigedig, moliant iddo Ef', 'Blessed one, praise be to Him', so it just borrows the tune from Lennon/McCartney. But I'm not up to transcribing it.
I'm currently learning Welsh but am not up to transcription level yet! I have been looking at lyric sites & have both Y Lolfa '100 O Ganeuon' volumes but can't find this one. We currently play All My Loving in our uke group and I'm intrigued by this, as it's clearly not a literal translation of that number. It would be fun if I were able to sing this in Welsh if someone gets the time to transcribe it please. Diolch yn fawr.