In my days [0960-70s] it was said that a 'donkey engine' was originally called that because it was less than 'one horse power'! How true I of course cannot say. 'Hand power' was also known as 'Norwegian Steam' because, so the story goes, in the 'last days of sail, when most large iron barques had 'donkey engines' Norwegian & [by definition] all Scandihooligan vessels didn't!