They were so in love that he proposed after just six months.

proposed 是动词 propose 的过去式。propose 由前缀 pro-（表示"向前"）和词根 pose（来自拉丁语 ponere，意为"放置"）组成，字面意思是"向前放置"，引申为"提出建议、提议"。在感情关系中特指"求婚"这个具体行为。