During tough times, her presence was a source of great comfort.

comfort 是名词，来自动词 comfort（安慰、使舒适），指"安慰、慰藉"的感觉或状态。这个词由前缀 com-（表示"加强"）和词根 fort（力量）组成，字面意思是"给予力量"，引申为"安慰"。