to play around, to joke around, be delighted, maid servant
娭 centers on lighthearted, playful behavior, often associated with women: joking around, being delighted, or playing. The maid servant sense is a specific historical application of a woman in a playful or attendant role.
娭 combines 女 (woman) with 矣, which likely contributes a sound element. The exact historical development is uncertain, but the character is associated with playful or delighted behavior.
A woman (女) beside 矣, which looks like a person with a big nose and a playful stance. Picture a woman joking around and being delighted, like a playful maid servant entertaining others.
For キ, imagine a key (キー) to a playful mood: the woman uses a key to unlock a box of jokes and delights. Key -> キ.