This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
紒 combines 糸 (thread) with 介, but the exact historical development and original meaning are uncertain.
With no clear meaning, picture a tangled thread (糸) caught between two people (介) — a confusing knot that resists interpretation.
For ケイ, imagine a tangled thread shaped like the letter K, and you say 'K, eh?' as you try to untie it: K-eh -> ケイ.