Salted herring roe, kazu no ko, has been a staple of northern climate native fishing populations for as long as man has been casting a net into the ocean. Tribal groups in Alaska, aboriginal Scandinavians and the indigenous groups of Northern Japan have long considered this preserved food a delicacy, as well as a vital source of nutrients, to be eaten during the cold months of winter.
The Yamato people — today's majority ethnic Japanese population — record kazu no ko as being eaten earliest in 1477. References become frequent enough by the 17th century to consider herring roe an important foodstuff. By the 19th century, cooks had clearly made kazu no ko part of the New Year's table throughout the country — imported to the western and southern parts of Japan from the cold waters off the coast of Hokkaido.
The name kazu no ko comes from the Yamato word for herring roe, kado no ko. Kado, for herring, and the word for children, ko, also used to mean egg, especially fish roe. Change kado to kazu — numerous, a multitude — and the name for salted fish eggs becomes eloquent and literary — requirements for any important Japanese foodstuff. Because of the use of kazu no ko on auspicious occasions, such as the o-shogatsu (New Year's) holiday, and this play on words, the placement of simple roe on the table becomes a benediction for the blessing of many children in many generations.