Source: Classical literature
Fesin-i toldohon is the Manchu word for the ferrule on a sword grip, as it turns up in a 1766 dictionary.1 The ferrule prevents the hilt from splitting and provides a tight fit against the guard.
Fesin literally means: handle, stock, grip, or pole for a flag or banner.2
Toldohon literally means: an engraved band or ring on the hilt of a sword or dagger.3
For a complete overview, see: A Manchu saber glossary.
A Chinese saber ferrule of the round style. Late 18th / early 19th century.
1. Terms are taken from the Wuti Qingwen Jian (五體清文鑑) or "Five languages compendium", a Qing imperial dictionary in Manchu, Mongolian, Uighur, Tibetan and Chinese of 1766.
2. Jerry Norman; A comprehensive Manchu-English dictionary. Harvard-Yenching Institute Monograph Series 85, Harvard University Asia Center, Cambridge (Massachusetts) and London, 2013.