土

It is a pictograph modeled after a heap of soil on the ground.

For reference, the character representing a sprout growing from the ground is 生 (to grow, to be born).

Historically, 土 is one of the Five Elements (오행) and has been considered very important.

It is mutually generating (상생) with 火 (fire) and 金 (metal), but conflicting (상극) with 木 (wood) and 水 (water).

土 is easily confused with 士 (scholar), but 士 means “scholar” or “gentleman.”