become toughened

His life had been one of hardship and privation, as street life always is, but he had become toughened to it, and bore it with a certain stoicism, never complaining, but often joking in a rude way at what would have depressed and discouraged a more sensitive temperament.

Dried apples are much inferior to the fresh fruit, because they become toughened in drying, and because growers sometimes smoke them with fumes of sulphur in the process, in order to bleach or whiten them; and this turns them into a sort of vegetable leather.

A bachelor, Anderson had become toughened by hotel and pension.