brave
朅 centers on bravery and boldness. It is a rare kanji with a single clear meaning.
朅 combines 去 (go away) with 曷, which may contribute a sound element. The exact historical development of the meaning 'brave' from these components is uncertain.
The left side 去 suggests going forward, and the right side 曷 looks like a bold, complex structure. Picture a brave warrior striding forward into a tangled challenge.
For ケツ, imagine a brave warrior letting out a sharp ketsu! battle cry as they charge forward: ketsu -> ケツ.