The Oxford University Press made the claim after analysing more than 130,000 children's stories submitted for BBC Radio 2's annual story-writing competition 500 Words.
The US president's name came up more than any other - suggesting how much Donald Trump's larger-than-life personality has become part of UK children's literary imaginations.
But the presidential name has been used in many unfamiliar settings, creating new words and characters, such as Boggle Trump, Snozzle Trump, Trumplestilskin and Trumpyness.
The short stories also display a satirical ear for President Trump's use language.
A Trump-related tale of space travel includes the boast: "I am going to make the Moon great again!"
The final of 500 Words is being presented by Chris Evans from the Tower of London on Friday, when the overall winners will be revealed in the categories for writers aged five to nine and those aged 10 to 13.
Perhaps reflecting the wave of elections and votes, the word "politics" has itself become more commonly used by children entering the competition and there were references to "fake news" and "Brexit".
Social media networks such as Snapchat and Instagram are also frequently mentioned.
Another widely used term was "super", whether it was characters who were "super-excited" or "super-happy" or many variants of "superhero".
The language of old-fashioned superheroes also seems to have survived.
In the tradition of Batman, there are still sounds of "ka-pow!" and "arrrghhh!" But so far, no signs of "bigly."
His name is never out of the headlines, and "Trump" now seems to have taken over the playground too - as it is named children's "word of the year".