India, Sept. 23 -- President Donald Trump's Rose Garden briefing on autism spectrum disorder (ASD) shifted focus Monday when he stumbled over the word "acetaminophen," the common pain reliever in Tylenol. The event was promoted as a "major advance" in autism research, highlighting new evidence about prenatal Tylenol use and higher autism risk, but the brief slip became the main headline.

In front of reporters and officials, Trump paused over his notes and tried to pronounce it. "Ah-ced-uv. well, let's see how we say that. Ascenem - enophin. Acetaminophen. Is that ok?" he said, drawing laughs in the crowd. Within minutes, clips spread online and were compared with his earlier verbal gaffes, such as calling Yosemite "yo-Semites" back in 20...