The “holy tongue” is Hebrew. Aramaic is secondarily holy because the Gemara was written in it.
Yiddish when it was spoken as the daily language of most Ashkenazi Jews was no more holy than English is in the US today. It had plenty of not so holy uses the same as any spoken language. The Forvetz (Forward), was at one time one of the most anti-religious newspapers in NYC, and it was published in Yiddish. (Now it’s not anti-religious, just non-religious, and it’s printed in English.)
In the US and – I believe – in Israel there has been a dispute because when the first Torah-observant immigrants came from Europe, they learned Torah in Yiddish because that was their mother tongue and some Gedolim insist that the tradition be carried on. Other Gedolim here in the US, such as Reb Moshe zatzal and Reb Yaakov zatzal, poskened that children should be taught Torah in the language they think in. For most students in the US outside of BP and Willy that would mean English.
So is Yiddish holy? Depends on who you ask. It’s all a matter of history.