depend upon, support, go against, (variant deceive)
佹 centers on a relationship of leaning or turning: depending on or supporting someone, or conversely going against them. The variant sense of deceiving fits as a dishonest turning away from truth.
佹 combines 亻 (person) with 危, which likely contributes both sound and the idea of danger or leaning. The exact historical development is uncertain, but the character likely expressed a person in a precarious or dependent position.
A person 亻 leaning on something dangerous 危: depending on it for support, but also risking going against it or being deceived.
For キ, imagine a person depending on a key (キー) to unlock a dangerous situation: key -> キ, and the person 亻 leans on it for support.