耄耋

Both characters use the 老 (lǎo 'old') radical. 耄 (mào) traditionally meant about 70-90; 耋 (dié) meant about 70-80. Combined, 耄耋 is the literary cover-term for 'extreme old age,' typically eighties and nineties. Han Kang and Han dynasty texts already used both.

memory

A common pun: 耄耋 (màodié) sounds nearly like 猫蝶 (māodié, 'cat + butterfly'). Traditional paintings of cats and butterflies are auspicious gifts to elders precisely because they pun on 耄耋, wishing the recipient long life.