An idiot savant is a person who is considered to be mentally handicapped but displays brilliance in a specific area. Those with the condition generally have neuro-developmental disorders such as autism spectrum disorder or a brain injury. Savant skills are usually found in one or more of five major areas: art, memory, arithmetic, musical abilities, and spatial skills.
The term is used figuratively in a 📝Colloquial context to describe someone who has stumbled into success by virtue of their ignorance—unaware of what others consider common knowledge.