pustule (n.) Look up pustule at Dictionary.com
late 14c., from Old French pustule (13c.) and directly from Latin pustula "blister, pimple," from PIE imitative root *pu- (1) "blow, swell," on notion of "inflated area" (cognates: Sanskrit pupphusah "lung," Greek physa "breath, blast, wind, bubble," Lithuanian puciu "to blow, swell," Old Church Slavonic puchati "to blow"). Compare emphysema. Related: Pustulant; pustular.