Five thousand years ago, Proto-Indo-European speakers on the Pontic-Caspian steppe used the word brahter to mean "brother". Obviously this went on to evolve into words like English brother and Latin frater, but far more interesting was the term's development into Sanskrit, where it was spelled bhrata and meant the same thing. That further morphed into Romani phral or pral, which was brought into Europe by the migrating Roma around the thirteenth century CE. By 1770, the word was being used in English to refer to accomplices in crime (perhaps due to mistrust of the Roma), but by the middle of the nineteenth century, it lost all consonant clusters and took on a definition of "compatriot" or "friend" - the word pal as we know it today! The verb form was first attested in 1879.
Adam Aleksic, a freshman studying linguistics at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in words, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
The Etymology Nerd