it’s your mother tongue which you may not normally use because nobody in your area speaks it.
= = =
But the Holy Spirit knows it, and satan does not.
From your spirit to God, without your own human ‘understanding’ getting in the way.
How many languages do you think that Satan wouldn’t know or have access to?
Well, since Satan himself was once an unfallen angel, I would expect he's be familiar with any language that angels might speak.
Besides the idea that tongues is a language that Satan cannot understand has absolutely ZERO Scriptural support.
I don't know where that concept came from or who invented it, but it is NOT found in Scripture.