According to Rules

The idiom "the arm of the law" likely emerged from the idea that the law reaches out like an arm to maintain order and administer justice. The phrase is often used to describe the actions and interventions of law enforcement agencies, such as police officers, in maintaining order, upholding laws, and apprehending criminals. It can be used in news reports, legal discussions, and conversations about crime and punishment.

The origin of the idiom "the third degree" can be traced back to the early 20th century, specifically to the practices of police interrogation in the United States. It is widely believed to have originated in the realm of organized crime and the techniques used by law enforcement to extract information from suspects. This phrase is frequently utilized in crime dramas, legal thrillers, and discussions about law enforcement practices. It can also be used more broadly to describe any situation where individuals are subjected to intense scrutiny or relentless questioning, beyond the realm of law enforcement.

The idiom "behind bars" originated from the physical structure of prisons, where prisoners are confined within cells that are typically equipped with bars or solid doors. The use of bars as a means of imprisonment has been prevalent throughout history, dating back to ancient times. The phrase is used to refer to individuals who have been convicted of a crime and are serving a prison sentence or awaiting trial while being detained.

The origin of the idiom "by the book" draws from the idea of following instructions or guidelines found in a book or manual, which can be traced back to ancient times. This phrase may have gained prominence during the 19th century, as the use of written rules and regulations became more widespread in various fields. It is commonly used in discussions related to law, regulations, policies, and professional practices.

The origin of the idiom "dos and don'ts" can be traced back to the early 20th century, where it emerged as a concise way to express a set of guidelines or rules. The phrase is derived from the use of "dos" and "don'ts" as shorthand for "things to do" and "things not to do." It is commonly employed in areas such as etiquette, safety protocols, job training, educational settings, and general life advice.

The origin of the idiom "green light" can be traced back to the early 20th century, specifically to the traffic signal system. The use of red, yellow, and green lights in traffic signals was introduced to regulate and control vehicular movement. The green light, being the third and final signal in the sequence, indicated that it was safe for drivers to proceed. This phrase is frequently used in business settings, project management, decision-making processes, and personal endeavors.

The origin of the idiom "rule of the thumb" is not definitively known, but it is believed to have originated in the 17th century. It is believed to have derived from an old English law that permitted a man to beat his wife with a stick as long as it was no thicker than his thumb. This phrase has been in use since the 17th century, with one of the earliest recorded instances found in a book by Sir William Hope in 1692. It is used in various contexts and occasions where a practical, general guideline or estimate is needed.

The idiom "clean bill of health" has its origin in the 17th century, when sailors were required to produce a document called a "bill of health" before entering a port. Over time, the phrase came to be used in contexts, such as in business, finance, or sports, to indicate that something has been found to be in good condition or free from any problems or issues.