Definition of the word check into

The expression "check into" has its origins in the context of hotels and lodging accommodations. In the late 19th century, hotels introduced a registration process where guests would present themselves at a front desk, provide identification, and pay for their stay, receiving in return a key to their room. The person at the desk would record the guest's name and other details in a "register" or "logbook," marking the time of the guest's arrival. The phrase "check into" emerged as a concise and familiar way to describe this process. It signified that the guest was not merely arriving at the hotel, but being officially registered and assigned to a specific room. This usage was quickly adopted by other industries and contexts where the idea of registration, confirmation, and assignation is relevant, such as booking a flight, reserving a table in a restaurant, or admitting oneself to a medical facility for treatment.