Also known as gokenjo (literally meaning 'widow woman'), because the flat shell resembles a bivalve shell but as it does not have a matching shell it can be compared to a widow who has lost her husband.
別名ゴケンジョ「後家の女」の意で、平たい貝殻が二枚貝の殻に似ているにもかかわらず、1枚しかないありさまを夫を失った未亡人（後家）に例えたもの。