Japanese dock (Rumex japonicus)
Archaic name for a plant; modern Japanese uses 羊蹄 (ようてい) or other names. Found in old botanical or literary contexts.
See also: ギシギシ
Old herbal texts record 'shibukusa' as a kind of Japanese dock.
The derivation is uncertain; the kanji 渋 (astringent) and 草 (grass) likely describe the plant's taste or use.