bias
BY-uhs · noun
Origin
Bias entered English around 1520 meaning an oblique line, borrowed from Middle French biais, which was used adverbially to mean 'sideways, askance, against the grain' as early as 1250. The French word likely traces to Old Occitan biais, of obscure origin, possibly from Vulgar Latin biaxius, 'with two axes.'
Journey
The word first described a literal slanted line in English, then around 1560 became a technical term in the game of bowls for the lopsided weighting that makes a ball curve. By about 1570, that curving tendency gave rise to the figurative sense of a mental slant or leaning we use today.
Related words
The facts don't support tracing bias to any specific English cognate, though its root idea, of having two axes, points to a word literally built from two directions.