What is the origin of the idiom "have a soft spot for somebody or something" and when to use it?

The origin of the idiom "have a soft spot for somebody or something" is not specifically known, but it likely originated from the figurative use of the word "soft" to describe a tender or gentle feeling towards someone or something. The idiom implies that there is a specific area in one's heart that is emotionally sensitive and receptive to a particular person or thing. It signifies feeling a particular fondness, affection, or sympathy towards them.