idiot savant
noun
- (often offensive) a person with savant syndrome; a savant
- a person who is highly knowledgeable about one subject but knows little about anything else
Wiktionary
noun
Etymology: From French idiot savant, literally ‘wise idiot’.
- A person who exhibits an extraordinary ability in one subject (often mathematics) whilst being intellectually disabled in many other domains.
“The temptation is to regard him [John Ogdon] as an idiot savant, a big talent bottled inside a recalcitrant body and accompanied by a personality that seems not just unremarkable, but almost entirely blank.”