means Covered with or soaked in water or another liquid; not dry.

from From Old English wǣt, tracing back to the same ancient root that gives us 'water' — a kinship you can feel. It's a deep Germanic word, cousin to Old Norse vátr, and ultimately part of a Proto-Indo-European family clustered around the idea of wetness and damp. In other words, 'wet' has been dripping its way through English since before English was quite itself.