Sources of "morality of results" in mathematics

Moralement literally means "In a manner consistent with the rules of morality". It is commonly used by French mathematicians with the meaning "In a manner consistent with the rules of mathematics". Whether mathematics are moral or not is another story...

I do not know the origin of this expression, this is an interesting question.

Edit. Just found the following references from the Dictionnaire de L'Académie française, 1st Edition (1694):

On dit, Moralement parlant, pour dire, Vraysemblablement & selon toutes les apparences.

Dictionnaire de L'Académie française, 4th Edition (1762):

On dit, Moralement parlant, pour dire, Vraisemblablement & selon toutes les apparences. Cela est vrai moralement parlant.

This is very close to the mathematical use of this word.