strengthen (part of speech: verb)
- Never frighten a child by throwing cold water on it or by giving it a too sudden cold plunge; great harm may be permanently done by these efforts to " toughen the baby." - "The Mother and Her Child", William S. Sadler Lena K. Sadler.
- It seems a very comfortable and sensible way to ride, but I shall have to toughen up a bit before I hit the trail for any length of time. - "The Prairie Wife", Arthur Stringer.
- I'll toughen up out here and have better wind for the big finish when I sit in on the old man's money. - "The Flockmaster of Poison Creek", George W. Ogden.