your mother tongue

the/(one's) mother tongue

The native language of one's home country. I love coming to the area where all the expats live. Even though I am fluent in Japanese and love speaking it, it's nice to hear the mother tongue now and again. It's shameful how you have turned your back on your culture and heritage—your children don't even know their mother tongue!
See also: mother, tongue

your ˌmother ˈtongue

the language you first learned to speak as a child; your native language: She was born in Singapore, but her mother tongue is French.
See also: mother, tongue
References in classic literature ?
Gliddon- and you, Silk -- who have travelled and resided in Egypt until one might imagine you to the manner born -- you, I say who have been so much among us that you speak Egyptian fully as well, I think, as you write your mother tongue -- you, whom I have always been led to regard as the firm friend of the mummies -- I really did anticipate more gentlemanly conduct from you.
I think your mother tongue is something that shouldn't be forgotten.
I believe that knowing your mother tongue and teaching it to future generations is important.
Holding on to your mother tongue is a practice that is needed.
If you want to learn your mother tongue, this can be done; there are no obstacles in the way of that.