Short answers, pulled from the story.
The Latin name for the weasel is Mustela, which literally translates to mouse javelin. This name reflects the animal's hunting style that relies on speed and precision similar to a thrown spear.
A taxonomic review in 1999 moved the American mink and extinct sea mink to the new genus Neovison. The changes continued into 2021 when the long-tailed weasel, Amazon weasel, and Colombian weasel were moved to the genus Neogale.
Non-native populations of the least weasel and stoat cause significant ecological damage in New Zealand. These populations prey on native bird species that have no evolved defenses against such agile predators.
In Greek culture, a weasel near one's house was considered a sign of bad luck or evil, especially if there was a girl about to be married. The animal was thought to be an unhappy bride who had been transformed into a weasel and delighted in destroying wedding dresses.
Kamaitachi is a phenomenon wherein one who is idle is suddenly injured as if his or her skin were cut by a scythe. In the past, this was thought to be the deed of an invisible yōkai weasel.