The idiom "faux pas" is French in origin and literally means "false step". In English, it refers to a social blunder or an error in behavior that can be considered inappropriate or offensive.

The idiom "buy time" means to purchase a short amount of time in order to gain more time or delay an action or decision that is urgent or important. It can also mean to get some additional time to complete a task, overcome a problem, or make a final decision.

The idiom "up to no good" is used to describe someone or something that is causing trouble or behaving in a dishonest or malicious way. It can also be used to describe a situation or event that is not desirable or positive.

The idiom "crash course" refers to a rapid, intensive, and comprehensive learning experience that covers all the important topics or skills necessary for a particular activity or goal.

The idiom "knight in shining armor" refers to a person who arrives unexpectedly and saves the day, often in a heroic or impressive way. It can also refer to someone who is exceptionally competent or capable at something.