"face only a mother could love"の定義と意味

What is the origin of the idiom "face only a mother could love" and when to use it?

The origin of the idiom "a face only a mother could love" is rooted in the concept of maternal love and the idea that a mother's affection for her child is unconditional. It is used to describe someone's appearance as unattractive or less appealing to most people. It conveys the idea that the person's looks are not universally considered attractive. The idiom is typically used in a lighthearted or teasing manner and is not meant to be offensive. However, it is important to consider the sensitivity and relationship with the person being referred to before using this idiom.