Tongue is a funny word for language and it tends to travel across languages, too. Language and tongue, are in fact, the same words in some languages.
But here – I think Horatio isn’t using the word tongue as language – he’s using it more literally. Because Hamlet and Osric are both speaking English, however arch and verified – but it may SOUND like another language. And I suspect that Horatio is attempting a bit of double meaning with tongue in that capacity.
I don’t think Horatio’s particularly funny, though, or all that quick with words. He’s a better listener than talker.
It is also odd that he pipes up to speak in just this moment.
Has Osric turned to him to get a translation?