AITKEN'S: from Aitken's Bakery, Aberdeen – I've found it on the Internet spelled sometimes with, and sometimes without, an apostrophe—but the owners are David Aitken and Beverley Aitken. You be the judge.

ROWIE: from the diminutive form of 'row' which in Scots means 'roll'

Here's an article about Aberdeen rowies.

From a University of Aberdeen media release:

"Although Ian [Pirie] has only been performing at Aberdeen TMSA events for the past six years, his singing and song writing skills go back to the early 1960s, when he was at school. During his time in Germany with the armed forces in the 1970s, his talents flourished and he was a regular performer at the folk club there. The themes of his songs are eclectic, ranging from a lament for the original Ferguson tractor and a song in praise of Aberdeen rolls, to 'A Fine Contented Man', which was written in memory of Tam Reid."

Further information about Ian Pirie is harder to come by.

There is an Ian Pirie who is an actor, a member of the Royal Shakespeare Company, who has appeared in several musicals. He was born in Aberdeen in 1966. I couldn't find anything at his web site about Aitken's or rowies or songwriting. Also, the dates don't match, so I doubt that he is the same person.

There is a Professor Ian Pirie who is a potter and a member of the craftscotland Board, but I also doubt that he's the same person.