Unknown. Widely, though incorrectly, believed to be an acronym for "Non-Educated [sic] Delinquent" although this is in fact a backronym
and folk etymology. Several other suggestions include a contraction of ne'er-do-well
, and some kind of relationship with Teddy Boy although its use much predates the 1950s origin of that phrase. Ostensibly unrelated to "Ned" as a diminutive
of the personal name "Edward" but the Scottish use of 'ned' for hooligan or lout is cited by the Oxford English Dictionary as dating from the early 19th century. The OED also attributes a possible derivation from the 'Edward' diminutive.