Green’s Dictionary of Slang

OTL n.

[song ‘Only the Lonely’ composed by Roy Orbison and Joe Melson(1960) ]

(N.Z. prison) one who spends most of their time staying in the cell.

[NZ]D. Looser Boobslang [U. Canterbury D.Phil. thesis] 132/1: OTL abbr. Only The Lonely, an antisocial inmate who spends much of her time in her cell.