Joomla! broke off from Mambo amid concerns over the open source nature of the project and then-CEO Peter Lamont took great care to get user feedback on how the project should be run going forward. Internet users at the OpenSourceMatters website offered support for the new project and in early September of 2005, Joomla! was born. The name itself came after the company asked for feedback from internet users on what the new project should be called. The name comes from the Arabic for "all together", which is an important idea for this web design project.
September 7, 2005 was the original release date of the first Joomla! interface and it was received with great reviews. Since then, it has been an absolute pioneer in the field of open source design, providing web designers with the opportunity to do things their way. Many companies have tried to follow the Joomla! blueprint, as more and more web users come to recognize the excellent potential that the company has brought to pass. Numerous updates to Joomla! have been released since 2005, with the most recent being July 22, 2009. According to reports, Joomla! is now the internet's most popular open source design portal.
Source: http://analogik.org