To distinguish it from the 16-bit system, the 32-bit operating system was sometimes EPOC32. Technologically, it was a major departure from the 16-bit incarnation (which came to be called EPOC16 or SIBO). In 1998, the 32-bit version was renamed Symbian OS. After Nokia acquired the rights to Symbian in 2010, they published Symbian's source code under the Eclipse Public License. In 2011, Nokia rescinded the open-source license for subsequent releases of the software.
Initially the operating system was capitalised as Epoc rather than 'EPOC', since it is not an acronym. The change to all capital letters was made on the recommendation of Psion's marketing department. Thereafter, a rumour circulated in the technical press that EPOC was an acronym for "Electronic Piece of Cheese". When Psion started developing a 32-bit operating system in 1994, they kept it under the EPOC brand. To avoid confusion within the company, they started calling the old system EPOC16, and the new one EPOC32. Then it became conventional within the company to refer to EPOC16 as SIBO, which was the codename of Psion's 16-bit mobile computing initiative. This change freed them use the name EPOC for EPOC32.
In June 1998, Psion formed a limited company with the telecommunications corporations Nokia, Ericsson, and Motorola. By buying into Symbian Ltd.—as the new company was called—the telecommunications corporations each acquired a stake in Psion's EPOC operating system and other intellectual property. Symbian Ltd. changed the name of EPOC/EPOC32 to Symbian OS, which debuted in November 2000 on the Nokia 9210 Communicator smartphone.
EPOC was developed at Psion, a software and mobile-device company founded in London in 1980. The company released its first pocket computer in 1984: an 8-bit device called the Psion Organiser. In 1986 they released a series of improved models under the Organiser II brand, but the 8-bit era was ending. Psion saw a need to develop a 16-bit operating system to drive their next generation of devices. First, however, they needed to engineer a 16-bit single-board computer—something that was extremely difficult at the time. They codenamed the project SIBO, for "single-board organiser" or "sixteen-bit organiser". To develop the SIBO hardware and software, they needed samples of the 16-bit microprocessors they would be programming; but it took more than a year to secure the chips, which caused a significant delay.