An "Off-By-One" (OBO) in a non-programming context is the act of a touch-typist beginning to type with their hands one key offset from home position.
If the typist in question types fast enough, the resulting nonsense string of gibberish resembling a 14 year-old's SMS history or YouTube comment may actually be sent/submitted before they notice what they've done.
Sm "Pgg-Nu-Pmr" )PNP_ om s mpm-ptphts,,omg vpmyrcy od yjr svy pg s ypivj-yupody nrhommomh yp yupr eoyj yjrot jsmfd pmr lru pggdry gtp, yjr jp,r ppdoyopm/ (*That was actually harder than I thought it'd be, though notice the prevalence of things like omg and gtp)
Carly1992: Wanna come over to my place?
TCAPreditorBate: totally* Sorry, off by one