It is the linguistic quirk of a self-styled tough guy with a bleeding heart for the poor.
President Rodrigo Duterte uses "putangina", a Tagalog slang for "w**** mother", as if it is an exclamation point, a conjunction when he abruptly shifts to a new topic, or as an ellipsis when he forgets what he is saying.
Usually, it is not directed at anyone. Sometimes, though, it finds its mark. He has used it on the Pope and the United States envoy to Manila. That fondness for this expletive is part of an image that has made Mr Duterte one of the Philippines' most successful politicians.
When he was campaigning, his audience would wait for him to blurt out "putangina", and then roar with laughter and approval. It was his verbal jab at what he saw as the phoney manners of a greedy elite, and voters gladly marched to his clarion call and handed him the presidency.
But on Monday, he may have gone too far. During a news conference, he laced a reply he gave to a reporter with his favourite expletive and directed it at one of the world's most admired leaders: US President Barack Obama.
Bristling when asked how he would respond should Mr Obama discuss with him his anti-crime war, which has left in its wake more than 2,400 dead bodies in over two months, he blurted: "Putangina."
He later apologised after the White House called off a planned bilateral meeting on the sidelines of the Asean summit in Laos.
It was a rude awakening for a man used to having his way.
Mr Duterte is quickly learning that when it comes to diplomacy, every word carries weight. "Words matter," said US State Department spokesman Mark Toner.
Chiming in, Democratic presidential candidate Hillary Clinton told reporters on her campaign plane: "There has to be a certain level of respect that is expected on both sides."
But it is proving to be a steep learning curve for the volatile and impulsive Mr Duterte.
"He is an iconoclast, and he's 71 years old. If we're thinking that there's a likelihood that he will change, he will not," said University of the Philippines political science professor Clarita Carlos.
"Let's just accept him for what he is, and let's just hope he will be more prudent in his articulations now that he is the President of the republic," she added.
The stakes, though, are too high to be left to Mr Duterte's willingness to change, especially with the Philippines taking over the chairmanship of Asean next year.
"I'm afraid that if we continue this kind of course, we might be isolating ourselves from the rest of the world," said lawmaker Raul Daza.
Mr Duterte is coming off as a petulant, unpredictable leader, and it is unnerving investors.
"The latest incident raises concern that President Duterte's unpredictable behaviour in politics will be disruptive and could eventually spill into economics and business," Mr Jonathan Ravelas, chief market strategist at BDO Unibank, told Bloomberg.
Local stocks have seen a pullout by foreign money in recent days. The key index dropped for a third day, and is on course for the biggest decline in a month.
But Mr Richard Javad Heydarian, a political analyst at De La Salle University, believes that, stripped of the incendiary rhetorics, "there is a seismic and fundamental change happening here".
"We are entering a new normal relationship with the US: still strong, but no longer as special," he said.
Mr Duterte has been seeking to mend ties with China, frayed by his predecessor's confrontational stance over maritime claims in the South China Sea.
That "soft landing" approach has been a concern for the US, but it is winning Mr Duterte key support within Asean, said Mr Heydarian.
"People appreciate the fact that he's no longer the China hawk in Asean," he added.
Still, Mr Heydarian and others agree that Mr Duterte would have to learn to tone down on the gutter language. Said Mr Lauro Baja, former Philippine permanent representative to the United Nations: "The onus is on his adviser."
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