I’ve flagged your comment because it’s essentially inviting a flame war, on top of being utterly irrelevant to the topic.

10 seconds on Wikipedia would have answered your question by the way. https://en.m.wikipedia.org/wiki/French_mother_sauces

The reason is that “sauce” is feminine in French. Une sauce. C’est tout.

You want to talk about pointlessly gendered, as a French native I agree that the French language, as most other Romance languages, Slavic languages and several Germanic ones, are all pointlessly gendered. I am envious of English natives that don’t have to deal with knowing that a chair is feminine but a stool is masculine, a bank is feminine but a shop is masculine. Or that a book is masculine in French but feminine in Russian, and it’s the other way around for the unknown gender of a domesticated animal!!!

Still I would invite you to learn more languages.

I'm a male, and I cook far more than any of my friends - male or female. I've no problem with a "mother sauce" and in fact the thought never crossed my mind.

It's because they're the very basic sauces that "give birth" to all the others. It's not because it's a sauce your mother used to make.

Which is not what GP was suggesting...

Though personally it seems a silly thing to get hung up on. I'd be more worried about the fact that for many the archetypical professional cook/chef is a man, and in fact men make up something like 75% of those who choose such a career, when it's abundantly clear that there are zero biological advantages to being male as a chef.

"Ancestor sauce" works fine for that and is less pointlessly gendered.

wouldn't that make it pointlessly ungendered? do you feel that gender is inherently bad?