Where do you put the "s"?

You learn something new every day, they do say.  Well, thanks to correspondence in my paper, I learned something new the other day.  The question raised was - why when the plural of court martial is courts martial, is the plural of governor-general not governors-general but governor-generals?  And the answer lies in the hyphen. Court martial is two words with, unusually for English, the adjective following the noun, and where this is so you pluralise the noun - in this case, court. Governor-general on the other hand, because it is hyphenated, is classed as a single word and pluralised in the normal way, by sticking an "s" on the end.