impeccable adj.

word-forming element meaning "not, opposite of, without" (also im-, il-, ir- by assimilation of -n- with following consonant, a tendency which began in later Latin), from Latin in- "not," cognate with Greek an-, Old English un-, all from PIE root *ne- "not."

In Old French and Middle English often en-, but most of these forms have not survived in Modern English, and the few that do (enemy, for instance) no longer are felt as negative. The rule of thumb in English has been to use in- with obviously Latin elements, un- with native or nativized ones.

"slight sin, petty crime or fault," 1590s (earlier in corrupt form peccadilian, 1520s), from Spanish pecadillo, diminutive of pecado "a sin," from Latin peccatum "a sin, fault, error," noun use of neuter past participle of peccare "to miss, mistake, make a mistake, do amiss; transgress, offend, be licentious, sin," a word of uncertain origin.

Watkins traces it to PIE *ped-ko-, suffixed form of *ped- "to walk, stumble, impair," from root *ped- "foot." But de Vaan is suspicious: "there is no reference to feet in the meaning of peccare. And to 'make a faux pas' ... would hardly be rendered by the word for 'foot', but rather by 'walking.' " He finds a derivation from the root *pet- "to fall" via *pet-ko- "a fall, error" to be "better semantically, but the addition of *-ko- to the bare root seems strange."

Proto-Indo-European root meaning "foot."

It forms all or part of: antipodes; apodal; Arthropoda; babouche; biped; brachiopod; cap-a-pie; centipede; cephalopod; cheliped; chiropodist; expedite; expedition; foot; foosball; fetch (v.); fetter; fetlock; gastropod; hexapod; impair; impede; impediment; impeach; impeccable; isopod; millipede; octopus; Oedipus; ornithopod; pajamas; pawn (n.2) "lowly chess piece;" peccadillo; peccant; peccavi; pedal; pedestrian; pedicel; pedicle; pedicure; pedigree; pedology; pedometer; peduncle; pejoration; pejorative; peon; pessimism; petiole; pew; Piedmont; piepowder; pilot; pinniped; pioneer; platypus; podiatry; podium; polyp; pseudopod; quadruped; sesquipedalian; stapes; talipes; tetrapod; Theropoda; trapezium; trapezoid; tripod; trivet; vamp (n.1) "upper part of a shoe or boot;" velocipede.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit pad-, accusative padam "foot;" Avestan pad-; Greek pos, Attic pous, genitive podos; Latin pes, genitive pedis "foot;" Lithuanian padas "sole," pėda "footstep;" Old English fot, German Fuß, Gothic fotus "foot."