ethics, morality, virtue
德 centers on inner moral character and right conduct: ethics, virtue, and the quality of being morally good.
德 is the traditional form of 徳. It combines 彳 (step/action) with a phonetic component that also suggests uprightness or moral quality. The right side historically includes 直 (straight) over 心 (heart), pointing to a straight heart as the source of virtue.
The left side 彳 suggests a path or action, and the right side contains 直 (straight) over 心 (heart). Picture walking a straight path with an upright heart: that is virtue and moral conduct.
For トク, imagine a person of virtue speaking about ethics: their talk (トーク, to-ku) is full of moral wisdom. Talk -> トク.