na-adjective, noun
Primarily used for children and pets; carries a warm, praising tone. Often used by parents or caregivers.
See also: 利口
うちの子は今日とてもお利口にしていた。
My child was very well-behaved today.
お利口な犬だね。
What a good dog you are.
利口 can mean clever or shrewd in addition to well-behaved; お利口 is softer and almost exclusively used for good behavior, especially of children and pets.
Honorific prefix お + 利口 (clever, well-behaved). The exact derivation of 利口 is uncertain, but it is conventionally associated with the meanings 'clever' and 'good'.