Common term for any truck produced by The Kenworth Motor Truck Company of Seattle - a division of the Pacific Car and Foundry Company (PACCAR), which also owns rival brand Peterbilt.
The company was formed in 1923 by Harry Kent and Edgar Worthington. They expanded to Canada in 1927. They began production of fire trucks in 1932, and pioneered the sleeper cab in 1935. Their vehicles and parts were important in WWII - they made B-17 parts (for Seattle neighbor Boeing) among other parts and vehicles. Over the years the company has continued to grow and expand into new markets construction, oil, and so on. Their trucks are often the "heavy haulers" of the trucking industry.