Of Scottish origin: Anglicized form of two different Gaelic names, Cinaed and Cainnech. The former was the Gaelic name of Kenneth mac Alpin (d. 858), first king of the united Picts and Scots. The latter survives today in Scotland as the common Gaelic name Coinneach. Since early in the 20th century Kenneth has been in regular use and enjoyed great popularity as a given name well beyond the borders of Scotland.
English and North German: from Middle English peper, piper, Middle Low German peper ‘pepper’, hence a metonymic occupational name for a spicer; alternatively, it may be a nickname for a small man (as if the size of a peppercorn) or one with a fiery temper, or for a dark-haired person (from the color of a peppercorn) or anecdotal for someone who paid a peppercorn rent.