pluck hair, tweezers
鑷 centers on a small metal tool for gripping and pulling: tweezers, especially for plucking hair.
鑷 combines 金 (metal) with 聶, which likely contributes the sound and relates to gripping or pinching. The exact historical development of 聶 is uncertain.
The left side 金 is metal, and the right side 聶 looks like three ears being pinched together. Imagine metal tweezers plucking hairs as if they were tiny ears.
For セツ, picture a set of tweezers: set -> セツ, and you use the metal tool to pluck a hair.