Origin

This character combines the radical for metal or mirror on the left with a sound hint on the right. The left part, meaning metal or mirror, points to the original sense of a polished metal mirror. The right part, 監, is a sound hint that tells you roughly how to pronounce the character. Over time, the character's meaning expanded from the physical mirror to metaphorical senses — a mirror lets you see yourself and learn from what you observe, so "鑑" came to mean taking warning from something or learning from an example. The connection between seeing your reflection and gaining insight is the key to understanding why a mirror character carries meanings about learning and caution.