sides of chariot were weapons
This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
輙 combines 車 (vehicle) with 取 (take). The exact historical development is uncertain, but it likely relates to chariot parts or fittings.
The left side 車 suggests a vehicle, and the right side 取 suggests taking or handling. Picture a chariot with side compartments for taking weapons.
For チョウ, imagine a long-serving chariot driver named Chou inspecting the weapon sides: Chou -> チョウ.