also: そじし
noun
meat along the spine; back flesh
Archaic term for the meat, flesh, or muscles running along the spine, especially of animals. Not used in modern Japanese; encountered only in historical or culinary texts.
古い文献に「膂宍」という語が見えるが、現代では使われない。
The word 膂宍 appears in old documents, but it is not used today.
Compound of 膂 (backbone) and 宍 (archaic variant of 肉, meat). The reading そしし (or そじし) is of uncertain origin; possibly a native Japanese compound predating widespread kanji use.