Never forget that there is more than one way of spelling Johnny (and that "Johnnie" is one of the less common options). Type something like johnny lad into the onsite search engine which you will find at the top of every page, and it will find for you

HEY HOW MY JOHNNY LAD

It seems that I posted the words myself some years ago. I wouldn't like to think that I'd wasted my time. I can add, now, that the song was got from Johnson's Scots Musical Museum, IV, 1792, 368 (number 357). It appeared there as Hey how Johnie Lad.