In ancient times, a man who reached twenty went through the capping ceremony.
Tips
history
From the 礼记 chapter 曲礼: at twenty a man is called 弱, 'weak', because he is not yet at full strength, and he is 冠, given the cap of an adult. A girl came of age at fifteen, her 笄年.
mistakes
冠 is guàn here, the verb 'to put on a cap', as in 冠礼. The noun 'hat' is guān.
