drab (n.) Look up drab at Dictionary.com
1680s, "color of natural, undyed cloth," from Middle French drap "cloth, piece of cloth" (see drape (v.)). Figurative sense is c.1880. Apparently not related to earlier word drab, meaning "a dirty, untidy woman" (1510s), "a prostitute" (1520s), which might be related to Irish drabog, Gaelic drabag "dirty woman," or perhaps it is connected with Low German drabbe "dirt;" compare drabble (Middle English drabelen) "to soil (something); trail in the mud or on the ground" (c.1400). Ultimately perhaps from PIE *dher- (1) "to make muddy." Meaning "small, petty debt" (the sense in dribs and drabs) is 1828, of uncertain connection to the other senses.