A seemingly upbeat sentiment, “Let’s go, Brandon!” is actually a stand-in for swearing at President Joe Biden. The chant has become conservative code for something more vulgar: “F— Joe Biden.”

It started at an Oct. 2 NASCAR race at the Talladega Superspeedway in Alabama. Brandon Brown had won his first Xfinity Series and was being interviewed by an NBC Sports reporter. The crowd behind him was chanting something at first difficult to make out.

The reporter suggested they were chanting, “Let’s go, Brandon” to cheer the driver. But it became increasingly clear they were shouting, “F—- Joe Biden!”

During the weeks to follow, the phrase has become a rallying cry of the right. When the president visited a construction site in suburban Chicago a few weeks ago to promote his vaccinate-or-test mandate, protesters deployed both three-word phrases. This past week, Biden’s motorcade was driving past a “Let’s Go Brandon” banner as the president passed through Plainfield, New Jersey.

On Friday morning on a Southwest flight from Houston to Albuquerque, the pilot signed off his greeting over the public address system with the phrase to audible gasps from some passengers. Southwest said in a statement that the airline “takes pride in providing a welcoming, comfortable, and respectful environment” and that “behavior from any individual that is divisive or offensive is not condoned.”

The Trump campaign is even cashing in on the newfound popularity of the phrase. For anyone donating $45 or more to the Trump campaign, they receive a “Let’s Go Brandon” t-shirt, according to an email sent out last week.

Separately, T-shirts are popping up in storefronts with the slogan and the NASCAR logo.

And as for the real Brandon, things haven’t been so great. He drives for a short-staffed, underfunded team owned by his father. And while that win — his first career victory — was huge for him, the team has long struggled for sponsorship and existing partners have not been marketing the driver since the slogan exploded.