The digital agency has a majority stake in the operation, which is already working with undisclosed existing Profero clients on at least two projects.
Its capabilities include listening to digital conversations, influencing important bloggers and managing clients' social media presences.
It will also provide accountability around how social media activity leads to visits to and conversions on client websites.
Watt joined Profero last October to work on the launch, which extends Profero's existing expertise in digital advertising, content creation, search engine optimisation and pay-per-click.
Profero's current clients include Western Union, COI, Lufthansa, Johnson & Johnson and Channel 4.
Nick Blunden, the new chief executive of Profero UK, said: "We all recognise the impact social media is having in determining the success of our client campaigns, so bringing a specialist team on board with unrivalled contacts, expertise and knowledge of the sector will help further differentiate Profero in an increasingly results driven market."
Yabber's name is derived from the Aboriginal word meaning to speak.