According to Rothwell historian/Town Goalkeeper Matty Otley the wild boar takes it's place due to John O'Gaunt himself killing the last one in Rothwell. This tale was taught to him in Rothwell Victoria Primary and has shades of the Jebbediah Springfield tale on The Simpsons. I think Matley's teacher was Ms Crabapple.
The white rose is to signify Yorkshire and the water on the crest relates to the somewhat extravagantly named River Dolphin which runs through Rothwell. To most the 'river' is called The Beck and Matty thinks that these days a more appropriate symbol would be a shopping trolley.
Which brings us to the swan, which Matty says is a celebration of everyone's favourite fight and a pint spot on a Friday night, The White Swan in Rothwell!