old, elderly
耋 centers on advanced age: being old or elderly. It describes a person who has reached a late stage of life.
耋 combines 老 (old) with 至, which likely contributes the sound. The character is used to refer to an elderly person.
The top part 老 means old, and the bottom part 至 looks like a person arriving at a destination. Picture an old person who has arrived at a very advanced age.
For テツ, imagine an old person with a pet turtle (テツ is close to the English word 'tets' as in 'tetrapod', but here use a turtle named Tetsu). The old person walks slowly with Tetsu the turtle: Tetsu -> テツ.