BOLT  , an O . Eng. word (compare Ger . Bolz, an arrow), for a "

quarrel" or cross-bow shaft, or the pin which fastened a door . From the swift flight of an arrow comes the verb " to bolt," as applied to a horse, &c., and such expressions as " bolt upright," meaning straight upright; also the American use of " bolt" for refusing to support a candidate nominated by one's own party . In the sense of a straight pin for a fastening, the word has come to mean various sorts of appliances . From the sense of " fastening together " is derived the use of the word " bolt " as a definite length (in a roll) of a fabric (40 ft. of canvas, &c.) . From another " bolt " or " boult," to sift (through O . Fr. buleter, from the Med .