salty
堿 centers on saltiness: a salty taste or quality. The given meaning is narrow, so the core idea is simply the property of being salty.
堿 combines 土 (earth) with 咸, which likely contributes the sound and may relate to saltiness or a salty substance found in the earth. The exact historical development is uncertain.
The left side is earth 土, and the right side 咸 looks like a container with a lid. Imagine digging salty earth from the ground and storing it in a container: 堿 means salty.
For カン, picture a can of salty earth: can -> カン, and the earth 土 on the left is full of salt.
—