The Chinese character to express 'kori' is one used after the establishment of Taiho Ritsuryo (Taiho Code, in 701) and, before that, a different character had been used as can be seen in written materials (mokkan; a long and narrow wood plate for writing with a brush) which was discovered.
「郡」（こおり）と言う用語が用いられるのは、大宝律令制定以降、それ以前は「評」（こおり）を使っていた文書（木簡類）が見つかっている。