Reefer comes from "refrigerated"...

Have you ever heard of Reefers?

Reefer comes from "refrigerated". Reefer containers are large temperature-controlled cabinets used for storing and transporting cargo that requires temperature control and monitoring, such as fruit, meat, dairy products, pharmaceutical products, among others.

They are also differentiated from normal containers by their white paint, which allows them to maintain a lower temperature, but also allows them to be identified more quickly.