The joking gesture came after the two Austrians, attending a meeting of engine manufacturers, had expressed some surprise at rumours of a perceived rift at the top of a dominant team celebrating retaining both world championships.
British media reported that Lauda, a triple world champion and stakeholder in the team, could walk out after Sunday's season-ending race at the Yas Marina circuit so bad were relations between them.
Mercedes insiders dismissed the reports, one light-heartedly pointing out that the two bosses were as much joined at the hip as the hand.
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Others pointed the finger at 'mischief-making' by Red Bull principal Christian Horner and Formula One supremo Bernie Ecclestone, who is also close to Lauda, as part of tough negotiations over engines.
Former champions Red Bull had sought Mercedes engines after falling out with Renault but were rebuffed, with the German manufacturer worried about helping a rival to beat them.
With Ferrari and Honda also rejecting approaches, Red Bull are now expected to continue with Renault-provided engines for at least another year.
"We have an agreement in place for next year...but unfortunately due to circumstances beyond our control we can’t announce exactly what that is," Horner had said on Friday.
"Perhaps Toto can tell you?," he added mischievously, the Austrian sitting next to him in the FIA news conference.
Lauda, despite his Mercedes allegiances, is a friend of Red Bull's billionaire owner Dietrich Mateschitz and of the Austrian energy drink company's motorsport consultant Helmut Marko, a former F1 racer and contemporary.
A free spirit who has continued with his role as a TV pundit despite his team duties, Lauda regularly has breakfast in the Red Bull hospitality with Marko and was there again on Friday when Horner held a brunch with British media.
The Austrians also frequently share a private plane, with Wolff sometimes joining them.
Lauda went to see Mateschitz in the early stages of Red Bull's approach for an engine supply and has said he was supportive, although denying ever shaking hands on a deal.
Ecclestone told reporters in Texas last month that Red Bull had thought they had one, however.
"They believed they shook on it. In Niki's case, when he left Dietrich he was just shaking hands to say goodbye. These things happen in big families," said the 85-year-old Briton.
(Reporting by Alan Baldwin, editing by Amlan Chakraborty)
