rival

Etymology

First recorded in the 1570s^[1][2] as “one who pursues the same object as another”,^[1] borrowed from Latin rīvālis (“rival in love; neighbour”),^[1][2] originally “one using the same stream as another”,^[3][2][4] from Latin rīvus (“stream, brook”),^[3][1] from Proto-Indo-European *rei- (“to run, flow”).^[1][3]

The OED explains the Latin word as originally meaning one living on the opposite bank of a stream from another.^[5] Merriam-Webster allows a borrowing via Middle French rival.^[2]

References

1. [1] [2] [3] [4] [5] Harper, Douglas, Online Etymology Dictionary, https://www.etymonline.com
2. [1] [2] [3] [4] Merriam-Webster's Collegiate Dictionary, Springfield, Mass.: Merriam-Webster
3. [1] [2] [3] The American Heritage Dictionary of the English Language, Boston: Houghton Mifflin
4. [1] Random House Webster's Unabridged Dictionary, New York: Random House
5. [1] Simpson, J. A.; Weiner, E. S. C., eds. (1989), The Oxford English Dictionary, 2nd ed., Oxford: Clarendon Press