Ponzu is a traditional Japanese table condiment or dipping sauce for seafood, steaks, tofu, etc. This citrus sauce blended with soy sauce is a must condiment for shabushabu, for the citrus flavor softens the smell of meats and seafood.

The word "ponzu" is made up of two components:"pon" and "su". "pon" comes from the Dutch word "pons", meaning "citrus juice", and "su" means "vinegar". This "vinegar" here should be interpreted not as merely "vinegar" but "sanbai-su", the equal mixture of vinegar, soy sauce and "mirin". ("mirin" is a rice vinegar, or non-alcohol "sake" for cooking) "sanbai" means "three cups". What I mean here is the creator of this condiment chose to blend citrus juice, which is sour, instead of just vinegar.