Only sporadic pointers have been made on the lexemeبور būr, both as “horse” and as “colour”, a comprehensive study having evaded the attention of the modern scholars.
The word būr may be considered under four different categories, three separate connotations and two detached etymologies: (1) as toponym, (2) a certain “number” (3) a category of “colour”, and (4) as a specific brand of “horse”.
This paper is intended to elucidate the following long lasting misapprehensions: (a) that the etymologies of būr “ten thousand; large number, myriad” is quite separate and completely detached from that of the “horse” and the “colour”; (b) that būr as a brand of “horse” or a category of “colour” is of the same root and etymology; (c) that the etymological association of būr with the colour of the rodent beaver, resulting in glosses of “rose”, “red”, “brown”, “red- brown” labels, or “bay horse” has been totally speculative, in spite of its passage from generation to generation, (d) that the būr “blond, yellow, amber” is of a provincial nature, and (e) that the original connotation of the lexeme būr when applied to a horse was indicative of a specific brand, and was not a simple synonym to the lexeme asp/asb, thus the nomenclature asp/asb was applied as common noun, while the lexeme bãr was used as proper noun.
Both of the glosses of bãr as “horse” and as “colour” have been wrongly placed under būz for almost a millennium, and subjected to entirely speculative etymologies.
In conclusion, the bona fide meanings of būr both as a brand of “horse” and an associated “colour” label evolved from the same Iranian route bar- and became known as “fast, agile, nimble, intelligent”, “blue roan” and “blue roan horse” − possibly originally applied to the well-known Nisaeans of ancient Media, the most famous horses of antiquity.
Finally, it is pointed out that the use of būr with the connotations of “horse” or “brand of horse” have completely disappeared from the current Persian vocabulary, while the lexeme būr is still used, mainly in the sense of “yellow” and “blond” as a loan from the Ossetic, and in the expression of بورشدن būr šudan “(to) become embarrassed; (to) blush”, the origins of which is not very clear.