This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 氒 is uncertain. It may be a variant or simplified form of an older character, but its origin is not well established.
Since the meaning is unclear, focus on the shape: 氏 (family) above 十 (ten). Imagine a family of ten trying to remember this obscure character.
For ケツ, imagine a family of ten (氏 + 十) deciding on a name, and they all agree on 'Ketsu' as a distinctive, made-up name: Ketsu -> ケツ.