piddle · noun, verb1
Unknown. Compare regional German piddlen, pitteln, pütteln, pühteln (“to pick at something, pick at one's food”), dialectal German Pitzel (“small effort, small task”). Alternatively, perhaps originally from paw or put + -le (suffix forming verbs involving continuous or repeated movement). In later use, a euphemistic diminutive of piss, though not directly related to it. The noun derives from the verb.
Piddle · proper noun2
Unknown, but probably an Anglo-Saxon word for small watercourse, as several Piddles have been found in England. One source says it comes from Old English pidele (“marsh or fen”). The word predates the modern noun or verb piddle.
Etymology from Wiktionary, CC BY-SA 4.0.