The past tense of Toughen is toughened.
verb. ['ˈtʌfən'] make tough or tougher.
1. Verb, base form This means it can dry out or toughen up if not cooked properly or if overcooked.
1. It's not our job to toughen our children up to face a cruel and heartless world. It's our job to raise children who will make the world a little less cruel and heartless. - L.R. Knost, Two Thousand Kisses a Day: Gentle Parenting Through the Ages and Stages
