小儿科 literally refers to pediatrics, the medical department for children. In everyday speech, it has developed several metaphorical meanings: something trivial or not worth serious attention (like 'kid's stuff' or 'a piece of cake'), and by extension, behavior that is childish, naive, or petty. It can also describe someone as stingy. It is used both as a noun and, colloquially, as an adjective, often carrying a dismissive or mildly derogatory tone.