carl - a peasant, a man of low birth

carle - noun. Scot. a strong, robust fellow, especially a strong manual laborer. a miser; an extremely thrifty person.

It's good to have that cleared up.
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I clicked on the Braes of Balquidder in the DT (see near the top of this page). At first I thought it was a strathspey, but then I noticed that it changes from 2/4 to 3/4 and back. This is an unusual tune for a folk song. Interesting!