She tells the September issue of Brit mag Sugar that the insider nickname comes from "our fave film, 'Step Brothers,' starring John C. Reilly and Will Ferrell.
Lovato says Cyrus has given her great advice on dealing with fame.
"Recently she sent me this four-page text message encouraging me and telling me she has faith in me. It was so inspiring and made me feel great – because I do get a bit overwhelmed by the paps sometimes."
RE the Jonas Brothers, Lovato says, "Everyone asks me if I fancy them but I totally don't!"
BTW, she recently broke up with Miley’s brother, Trace Cyrus.