The squabbling in Merkel's fractious centre-right coalition has boiled over in recent days, with members of the Bavarian conservative CSU party branding their pro-business Free Democrats allies "a bunch of amateurs" on health policy.
Meanwhile, Free Democrats described the CSU as a "wild sow" for what they deemed destructive input during a controversial health care debate.
And the glamorous rising star of German politics, the aristocratic Karl-Theodor zu Guttenberg, defence minister from the CSU, was reportedly branded "Rumpelstiltskin" - the treacherous and vicious dwarf in a famous fairy tale.
But the chancellor, often referred to herself, not always kindly, as "Mutti" meaning "Mummy," has now put her foot down.
Such mud-slinging is "unacceptable," she told the Frankfurter Allgemeine Zeitung newspaper on Friday.
Those engaged in name-calling "should not be surprised that respect for politics in general is sinking," she added.
It is not the only thing sinking. The popularity ratings of Merkel, four-times named the world's most powerful woman by Forbes magazine, have plunged recently, due in large part to bickering within the coalition.
For his part, Guttenberg made light of his new nickname, saying, according to the Bild daily, that he was pleased to be compared to Rumpelstiltskin, who had the highly useful skill of spinning gold from straw.
"If I could do that in the current budgetary situation, I would love to be Rumpelstiltskin," said Guttenberg, who, like all ministers, has been asked to make sweeping cuts given Germany's precarious fiscal state.