The phrase "common tongue" refers to a language that is widely spoken and understood by most people in a particular region or group. It means a language that many people use to communicate with each other easily. Full definition
The dating culture there has loads of differences, and even though our countries share a common tongue (no pun intended) and a lot of history, these distinctions just might surprise you. (businessinsider.com)
Look, when we say that God waited to send Jesus until there was a common tongue and a good road system, what we are also saying is that the only part of the world that God really cared about was the part under Roman rule (Most of Europe, Northern Africa, and Western Asia). (redeeminggod.com)
The Urban Dictionary, that YouTube of the common tongue, has added this new definition to its peer - built lexicon of up - to - the - minute slang (nymag.com)