pec·ca·dil·lo (pěk'ə-dĭl'ō) n.
pl.pec·ca·dil·loes or pec·ca·dil·los A small sin or fault.
[Spanish pecadillo, diminutive of pecado, sin, and Italian peccadiglio, diminutive of peccato, sin, both from Latin peccātum, from neuter of peccātus, past participle of peccāre, to sin; see ped- in Indo-European roots.]
"slight sin," 1591, from Sp. pecadillo, dim. of pecado "a sin," from L. peccatum "a sin, fault, error," from neut. pp. of peccare "to make a mistake, sin," of unknown origin.