go-between
妁 centers on the role of a go-between, someone who mediates or arranges connections between parties, especially in matchmaking.
妁 combines 女 (woman) with 勺, which likely contributes a phonetic element. The exact historical development is uncertain, but the character is associated with the idea of a female matchmaker or go-between.
A woman (女) with a ladle (勺) connecting two cups, like a matchmaker pouring tea to bring people together.
For シャク, imagine a matchmaker shaking hands to seal a deal: shake -> シャク, and the go-between makes the connection.