Hmmm....

My first recollection of the phrase predates "Plastic Jesus" it was a verse....

I don't care if it rains or freezes.
I am safe in the arms of Jesus
I am Jesus' little lamb
My bloody oath I am....

It was a song popular with NZ tramping clubs in the 50s, and went to a march rhythm, which would suggest WWII origins. Hmm..... the humming noise is sparse brain cells trying to communicate.....

Me father was the keeper of the Eddistone lighthouse
Slept with a mermaid one fine night
From this union there came three
Two were fishes and the other was me.

Ummmm... oh for me 1960 Varsity Songbook. Can't for the life of me think of any other verses. I'll sleep on it. However, even when singing the song, way back when, I had the feeling that I'd heard the first three lines from a gospel song.

Hope that 2dworth helps a bit.

G'night - Sam