FO

A phrase that was pretty common in the 1970s, which was several years before online chat was available.

The acronym FO can stand for "freaking out." If someone tells you that you're FO, they think you're stressing overmuch about something.

The phrase "freaking out" comes from 1960s counterculture, in which hippies and other LSD users used the term to mean having a negative reaction to their psychotropic drug of choice. From there, the term came to be applied to all sorts of other irrational, paranoid, or stress-related behavior.