Person from Wigan.
Nothing to do with the large number of pies eaten in Wigan but to do with a miner's strike in the 1920's when all the pits in WIgan and Leigh went on strike. The Wiganers went
back and
broke the strike, the "Leythers" continued to strike and
got better pay and conditions. Therefore the Wiganer's had to "eat humble pie"... so it's a term of abuse from Leythers to Wiganers. The hostility between the
two towns stretches back hundreds of years to the civil
war when Wigan was Royalists and Leigh were Parliamentarian and continues to this day.