They go back 8000-9000 years in the Near East. They are found in archaeological sites before that, but as is the case for cereal grains, it is difficult to sort out what is cultivated and what is not. Esau sold his birthright to Jacob for a bowl of lentils. By 2200 B.C., they appear in Egyptian tombs. They are especially high in protein.
Lentils are particularly important in India today.
They are drought resistant. In the U.S. mostly in Washington and Idaho in the Palouse Prairies. They go back at least 9000 years. They may have also come from Ethiopia and Central Asia. In the Middle Ages in Europe, dried peas made up a major part of the diet of peasants.