"Ita" refers to the wooden cedar boards on which kamaboko loaves used to be molded and steamed and grilled; "wasa" is short for wasabi.
This is an appetizer consisting of slices of high-grade kamaboko with wasabi horseradish and soy sauce. Goes also well with sake. Use the soy sauce and wasabi as a dip for the kamaboko slices. Eat chilled or at room temperature.
[Itawasa - Photo: Wikipedia]