Donald Trump is coming up on his first one hundred days in office, a conventional measure of the initial success of a new president going back to FDR. But with a thwarted agenda, palace intrigue, and some self-inflicted wounds, Trump is pushing back against the meaningfulness of this traditional 100-day benchmark. What’s a hundred days, after all? he’s asking. Etymologically, Trump may just have a point: The word hundred is a little trickier to reckon than you may think.