old age
耈 centers on advanced age and the state of being old. It refers to old age itself rather than a specific action or object.
耈 combines 老 (old) on top with 句 on the bottom. The 老 component directly conveys the meaning of old age, while 句 likely contributes a phonetic element. The exact historical development is uncertain, but the semantic role of 老 is clear.
The top component 老 means old, and the bottom 句 looks like a bent figure with a cane. Picture an elderly person leaning on a curved staff: 耈 represents old age.
For コウ, imagine an old person with a cane slowly walking and making a soft 'koh' sound with each step: koh -> コウ, and the sound echoes the slow pace of old age.