Language: Mandarin Chinese
Source: Classical literature
Description
Qiào kǒugū (鞘口箍) is the mouthpiece of a scabbard.1

Scabbard mouthpiece of the round style on a late Qing military pattern saber.

Scabbard mouthpiece of a late Qing straightsword.
Also see
For a complete overview of saber terminology, see: A Chinese saber glossary.
References
1. Gongbu Junqi Zeli (工部軍器則例) or "Regulations and precedents on military equipment for the Board of Works" of 1815. A Qing imperial text dealing with the details of arms manufacture.