The Full Form of POJO is Plain Old Java Object.

The term “POJO” initially denoted a Java object which does not follow any of the major Java object models, conventions, or frameworks; nowadays “POJO” may be used as an acronym for plain old JavaScript object as well, in which case the term denotes a JavaScript object of similar pedigree.

The term continues the pattern of older terms for technologies that do not use fancy new features, such as plain old Ruby object (PORO) in Ruby, plain old telephone service (POTS) in telephony and Plain Old Documentation (pod) in Perl. The equivalent to POJO on the .NET framework is plain Old CLR object (POCO). For PHP, it is plain old PHP object (POPO).

The POJO phenomenon has most likely gained widespread acceptance because of the need for a common and easily understood term that contrasts with complicated object frameworks.