As other have explained, hold luggage is another term for checked-in luggage, and designates luggage that will go into the hold of the plane (which you check-in/drop at the departure airport, and claim at the arrival airport).

The term "hold luggage" (or "checked baggage") is derived from the nautical and aviation term for the "hold," which is the large storage compartment located in the lower deck of a ship or an aircraft. Historically, the word "luggage" comes from the verb "lug" (meaning to pull or drag with effort), reflecting the heavy nature of these items. When you "check" your bags, they are placed in the aircraft's hold because they are too large, heavy, or hazardous to be kept in the passenger cabin. This separation ensures cabin safety and passenger comfort. In modern aviation, the "hold" is a pressurized and often temperature-controlled environment designed to safely transport everything from suitcases to oversized cargo and pets. This division allows airlines to maximize cabin space while utilizing the aircraft's structural underbelly for heavy lifting.