Complex sentence: Usage of the term peaked in the late 1980s, being mostly used to refer to BBS operators; someone doing equivalent functions on the Internet is primarily referred to as a "sysadmin", short for system administrator.
Split into simpler sentences: Usage of the term peaked in the late 1980s, mostly in reference to BBS operators. A person with equivalent functions on the Internet is typically called a "sysadmin", short for system administrator.