"'Alaaf' is the easiest to explain," says Georg Cornelissen, from the Institute of Regional Studies and History in Bonn.
The origin of the Cologne 'fool's call' - which today is also heard in Bonn and Aachen - is well-documented. Old clay jugs have been found in Cologne, dating back to around 1550, with "Allaf" written on them.
"This was a cheer, a drinking word that had nothing to do with carnival and meant 'may he live well'," the linguist explains.
Literally, "All af" meant alles ab - everything down, or everything else falls below it. The cry referred to the bishop, the mayor, or the Cologne region, so people also called "All af Kölle" - everything else under Cologne, meaning "Cologne above everything else". Today, people also call "Kölle Alaaf".
"There are technical reasons for the reversal," explains Cornelissen .
"Try it: 'Alaaf Kölle' is harder to shout than 'Kölle Alaaf'."
By the 19th century when Carnival became more organized with its own customs and traditional mockery of the authorities, the people celebrating referred to themselves as fools or jesters - Jecken - and made the call their own.
"We suspect that 'Alaaf' spread around Cologne at the expense of 'Helau'," says Cornelissen.
If you move away from Cologne, you soon meet the boundary where Alaaf becomes "Helau". This is the traditional cry in the carnival strongholds of Düsseldorf and Mainz, as well as in many other German cities.
However, as to its meaning, linguistic researchers are groping in the dark.
"With 'Helau' there are no reliable facts, only speculation," says Cornelissen.
Some of the possibilities include the idea that Helau could have its origins in the words Hellblau (light blue), Hallo or Halleluja, or that it may be a reference to the northern goddess Hel, who in winter opens the gate to her kingdom. The only certainty of Helau is that it expresses "the fun of joy", as Michael Euler-Schmidt, deputy director of the Cologne City Museum, explains.
In the Swabian-Alemannic language region in the southwest of the country, people yell "Narri-Narro", which simply means "I'm a fool, you're a fool".
In Saarland at the French border, they shout "Alleh hopp!", which according to language researcher Cornelissen is a phrase borrowed from French.
"Some of the battle calls have a proper history, they are derived from historical events or are deeply embedded in mythology," explains Euler-Schmidt.
"Many refer to the places where they are called. And sometimes it's just an expression; a saying that has always been used."
In Paderborn, North Rhine-Westphalia during carnival season, people shout "Hasi Palau", a call with its origins in the window of the city cathedral, which shows three hares - die Hasen in German.
"The 'Palau' is another form of 'Helau'," says Euler-Schmidt, explaining that it's a combination of Helau and Paderborn.
"Ahoi", on the other hand - which is used in Ludwigshafen am Rhein in Rhineland-Palatinate as well as in the Thuringian town of Wasungen - goes back to the late medieval moral satire play Das Narrenschiff (Ship of Fools) by Sebastian Brant.
Residents of Wuppertal call "Wupp-di-ka", in Regensburg they shout "Radi-Radi", and in the Bayreuth it's "Wau-Wau".
The number of carnival calls in Germany cannot be quantified, says Daniela Sandner, director of the German Carnival Museum in the Franconian town of Kitzingen.
"In fact, almost every village has its own," she says.
So the calls are about a feeling of home, a sense of belonging to a place. Carnival is a part of identity, just like other regional customs.
Many fools will goad each other with the fools' calls.
"These calls are a carnival ritual, but there's also something liberating about it," explains Sandner. "It is about leaving everyday life behind."
"You encourage others to participate, to be joyful, with the call," Euler-Schmidt says.
"And some of them, who may be showing signs of fatigue, are awakened again."