“Late Show” host Stephen Colbert thinks he knows the origin of the mysterious bruise that keeps turning up on President Donald Trump’s hand. The White House has said the bruise, which began appearing regularly earlier this year, is due to frequent handshaking and aspirin use.Trump often attempts to mask the mark with concealer: President Donald Trump's hands, seen on Aug. 25. The White House has said the bruising is due to frequent handshaking and aspirin use.Bloomberg via Getty ImagesBut Colbert spotted a report that tells a different possible story for how it appeared. According to Republican National Committee Chair Joe Gruters, Trump last year would eat McDonald’s as soon as he got to his plane after campaign events. “He had hot fries waiting for him from McDonald’s,” Gruters told the “Chambers, Changes & Conversations” podcast, saying they were handed to him as soon as he got on the plane.“Yes, he needs his McDonald’s fresh and piping hot,” Colbert said. “And he apparently pulls his Filet-O-Fish straight out of the fryer, which is why his hand looks like that.” See more in his Wednesday night monologue: Close