Factors behind the ubiquity of the eight bit byte include the popularity of the IBM System/360 architecture, introduced in the 1960s, and the 8-bit microprocessors, introduced in the 1970s. The term octet unambiguously specifies an eight-bit byte (such as in protocol definitions, for example)
Otherwise, people have tried with 12 bit byte. Varying byte length in PDP 10. 6, 7 and 9 bits in Univac computers.