Origin

The character 棟 combines the wood radical on the left, which classifies it as something made of timber, with 東 (east) on the right, which serves as a sound hint for pronunciation. The ridgepole is the main wooden beam that runs along the peak of a roof, so pairing "wood" with a phonetic component makes sense for naming this structural element. Over time, the character came to refer more broadly to the ridge of a roof or even a building itself.