1540s, "to peddle, to work in a trifling way," of uncertain origin, apparently a frequentative form. Meaning "to pick at one's food" is from 1610s; that of "urinate" is from 1796. Related: Piddled; piddler; piddling.
Meager; trivial; paltry: It was an effort, though a piddling one/ The case was ''a piddly little misdemeanor''/ Make your pissy-ass point again ( first form 1559+, second 1940s+)
[a euphemism for piss]