light, easy, simple, gentle
輕 centers on a lack of weight or burden: physically light, easy to do, simple in nature, or gentle in manner. The idea of lightness connects all these senses.
輕 combines 車 (vehicle) with 巠, which likely contributes the sound and the idea of something light or easy to move. The character originally referred to a light carriage.
A vehicle 車 that is light and easy to push: the right side 巠 looks like a streamlined frame, making the whole thing feel simple and gentle.
For ケイ, imagine a light kayak gliding easily on water: kayak -> ケイ, and the vehicle 車 is as light as that kayak.