seven islands
Refers to a group of seven islands, often used in proper names like 伊豆七島 (Izu Seven Islands).
The Izu Seven Islands are a chain of islands stretching south from Tokyo.
Shichito matgrass
A plant species (Cyperus malaccensis) used for making mats. Usually written in katakana as シチトウ.
Shichito matgrass is cultivated as a material for tatami facing.
Standard kanji spelling for the 'seven islands' sense.
Katakana spelling is usual for the plant name.
七 (seven) + 島 (island). The plant name is derived from the place name, as it was historically associated with the Izu Seven Islands.