Hiyayakko

Hiyayakko is a Japanese dish made with chilled tofu and toppings. The choice of toppings on the tofu vary among households and restaurants, but a standard combination is chopped green onion with katsuobushi (dried skipjack tuna flakes) and soy sauce. Other toppings include: Hiyayakko is also known as hiyakko or yakko-dōfu. Hiya means cold, and yakko refers to the servants of samurai during the Edo period in Japan. They wore a vest on which the "nail-puller crest" was attached, on the shoulders; therefore, cutting something (e.g. tofu) into cubes was called "cutting into yakko" (奴に切る, yakko ni kiru). "Hiyakkoi" or "hyakkoi", the Tokyo dialectal term equivalent to the standard Japanese "hiyayaka" (冷ややか), is also a possible etymology.

Source: Wikipedia