delicacy, purport

旨 is composed of 匕(dagger, ladle) and the variant of 口 (mouth). 匕 is a pictograph of a spoon or ladle, so 旨 depicts the image of a spoon putting food into the mouth, with its original meaning being delicious. How the food tastes in the mouth is something only oneself knows in their heart, so 旨 later also came to mean "purport".