What is to cause to become antiquated, rigid, or fixed, as by fossilization; to mummify; to deaden. Ten layers of birthdays on a woman's head Are apt to fossilize her girlish mirth. Mrs. Browning called?

fossilize — To cause to become antiquated, rigid, or fixed, as by fossilization; to mummify; to deaden. Ten layers of birthdays on a woman's head Are apt to fossilize her girlish mirth. Mrs. Browning. (Webster's 1913.)