Language: Mandarin Chinese
Origin of term: Collector's jargon
The yútóudāo (魚頭刀) or "fish head saber" is a subtype of Chinese sabers with fairly straight blade that sweeps up at the tip. The most characteristic of the type is that is has a peaked spine.
I have not been able to find the term in classic literature, but some yútóudāo seem to confirm the validity of the term by having eyes and gills engraved into their tips to make them appear more fish-like.
See a classic fish head saber with engraved gills and eyes on the website of Art Museum of Ancient Chinese Weapons.
A rather similar example that I sold in 2006.
Most yútóudāo seem to be quite early and date from the late Ming to Ming-Qing transition period.