(idiomatic) To be knowledgeable about, and competent at, a particular subject or task.

To understand one's rank or status and behave accordingly; to act humbly.

(idiomatic) retort to questioning about a person by a stranger, when one does not want to confirm or deny knowing or being the person.

Synonym of know B from a battledore (“to know anything at all; to have the most basic common sense or intelligence”)

(US, African-American Vernacular) Indicates complete agreement.

(set phrase) To understand completely.

(rhetorical) Indicates strong agreement with a preceding statement.

(chiefly upper Midwest US, informal) Used as a rhetorical question to confirm agreement, knowing or understanding at the end of a statement.

Alternative spelling of you-know-who

(idiomatic) Alternative form of wouldn't you know it