1520s, "oblique or diagonal line," from French biais "a slant, a slope, an oblique," also figuratively, "an expedient, means" (13c., originally in Old French a past-participle adjective, "sideways, askance, against the grain"), a word of unknown origin. Probably it came to French from Old Provençal biais, which has cognates in Old Catalan and Sardinian, and is possibly via Vulgar Latin *(e)bigassius from Greek epikarsios "athwart, crosswise, at an angle," from epi "upon" (see epi-) + karsios "oblique" (from PIE *krs-yo-, suffixed form of root *sker- (1) "to cut").
In the old game of bowls, it was a technical term used in reference to balls made with a greater weight on one side (1560s), causing them to curve toward one side; hence the figurative use "a one-sided tendency of the mind" (1570s), and, at first especially in law, "undue propensity or prejudice."
The bias of education, the bias of class-relationships, the bias of nationality, the political bias, the theological bias—these, added to the constitutional sympathies and antipathies, have much more influence in determining beliefs on social questions than has the small amount of evidence collected. [Herbert Spencer, "The Study of Sociology," 1873]
For what a man had rather were true he more readily believes. Therefore he rejects difficult things from impatience of research; sober things, because they narrow hope; the deeper things of nature, from superstition; the light of experience, from arrogance and pride, lest his mind should seem to be occupied with things mean and transitory; things not commonly believed, out of deference to the opinion of the vulgar. Numberless in short are the ways, and sometimes imperceptible, in which the affections colour and infect the understanding. [Francis Bacon, "Novum Organum," 1620]
c. 1600, "shield louse (Coccus ilicis) that yields a red dye" (1590s of the tree on which the insects live), from Medieval Latin cremesinus (also source of French kermès, Italian chermes, Spanish carmes), from Arabic qirmiz "kermes," from Sanskrit krmi-ja a compound meaning "(red dye) produced by a worm."
The Sanskrit compound is krmih "worm" (from PIE root *kwrmi- "worm," source also of Lithuanian kirmis, Old Irish cruim, Albanian krimp "worm") + -ja- "produced" (from PIE root *gene- "give birth, beget"). The insect lives in the Levant and southern Europe on a species of small evergreen oak (kermes oak) and in ancient Europe were the main source of red and scarlet dye. The dye is prepared from the dried bodies of pregnant females, which alive resemble small roundish grains about the size of peas and cling immobile to the tree on which they live. From this fact kermes dye was, for a long time, mistaken as being from a seed or excrescence of the tree, and the word for it in Greek was kokkos, literally "a grain, seed" (see cocco-). This was passed to Latin as coccum, coccus "berry [sic] yielding scarlet dye," in late use "scarlet color, scarlet garment."
So important was kermes (coccus) as a commercial source of scarlet dye that derivatives of the name for it have displaced the original word for "red" in many languages, such as Welsh coch (from Latin), Modern Greek kokkinos. Also compare Russian čcermnyj "purple-red," Old Church Slavonic čruminu. Compare also crimson (n.).
Kermes dyes have been found in burial wrappings in Anglo-Scandinavian York, but the use of kermes dyes seems to have been lost in Europe from the Dark Ages until early 15c. It fell out of use again with the introduction of cochineal (the word for which itself might be from coccus) from the New World.
Cloths dyed with kermes are of a deep red colour; and though much inferior in brilliancy to the scarlet cloths dyed with real Mexican cochineal, they retain the colour better and are less liable to stain. The tapestries of Brussels and other parts of Flanders, which have scarcely lost any thing of their original brilliancy, even after a lapse of 200 years, were all dyed with kermes. [W.T. Brande, "Dictionary of Science, Literature, & Art," London, 1842]