This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
嗋 combines 口 (mouth) with 脅, which likely contributes sound. The exact historical development is uncertain.
A mouth 口 beside 脅, a shape associated with threat or coercion. Imagine a threatening mouth that intimidates, but the exact meaning is unclear.
For キョウ, picture a loud, threatening shout echoing through Kyoto: Kyoto -> キョウ, and the mouth 口 amplifies the threat.