Obscure Vocabulary Break!
What the heck is a “Tanas”? Well, as it happens, that’s the wrong question. The word does exist and it means a sort of useless, indecisive person, but “O tanas” is also an exclamation indicating disagreement or disbelief, so something like “That’s what you think” or “No way!”, or, of you’re in a hurry, “Bollocks!”
It seems to hardly appear online. Priberam defines it but Linguee doesn’t know about it at all, so I’d say probably not one to whip out in the supermarket.
Luso 