I read it in a Hardy Boys book set in Canada and don’t know why this male character keeps saying it. Can a female use it as well?
Litterally it means “Good thunder”, it is an expression, i have never heard it before, it could be typical to Canada. I would assume that it means the same as the expression “Tonnerre de Brest” which translates by thunder from Brest (Brest is a city in France) and it would be like saying “Damned” or “Jeeez”
You also have the expression “du tonerre” it means fantastic.
I don’t see why not a female couldn’t use it, there is nothing wrong with it
Tonnerre De Brest Meaning
it is an expression!