hard, wise
臤 centers on the idea of being firm and unyielding, like something hard, and by extension, possessing deep, steadfast wisdom.
The exact historical development of 臤 is uncertain. It visually combines 臣 and 又, but the original semantic and phonetic roles of these components are not clearly established.
A strong minister (臣) with a firm hand (又) represents hardness and wisdom—unyielding in principle and sharp in judgment.
For カン, imagine a can made of hard metal, unbreakable and wise in its design: can -> カン.