Green’s Dictionary of Slang

one hundred percent soli n.

also one hundred percent uso
[Samoan soli, the boys, and uso, brother]

(N.Z. prison) a wholly supportive and trustworthy friend.

[NZ]D. Looser Boobslang [U. Canterbury D.Phil. thesis] 130/2: one hundred percent soli (alsoone hundred percent uso) n. someone totally loyal and supportive to his friend ].