By repeatedly watching horror movies, he underwent desensitization to scary scenes.

desensitization 是由前缀 de-（表示"去除"）和词根 sensitize（使敏感）加上名词后缀 -ation 构成。sensitize 来自形容词 sensitive（敏感的），所以 desensitization 字面意思是"去除敏感状态"，即"脱敏"的过程或结果。