There was the following paragraph in the article titled “Welcome to the post-truth presidency” in Washington Post (December 2).
“As Politico’s Susan Glasser wrote in a sobering assessment of election coverage for the Brookings Institution, “Even fact-checking perhaps the most untruthful candidate of our lifetime didn’t work; the more news outlets did it, the less the facts resonated.” So there is no reason to think Trump is about to suddenly truth-up. Indeed, all signs are to the contrary — most glaringly Trump’s chockfull-of-lies tweet that “I won the popular vote if you deduct the millions of people who voted illegally.”
Though Google Ngram indicates that the word, “truth up” is current even before or since the beginning of the 19th century with its peak of usage in mid-1800s, neither Oxford nor Cambridge online dictionaries carry this word.
Does “truth up” mean to try to be more truthful and show integrity? What does “truth up” mean? Is it a popular word?