Maminha is the traditional name in Brazil. Elsewhere, butchers sell the same piece — or a close cousin — under a different name.
Adjacent cuts on the same Brazilian alcatra primal — maminha is the lean tail, picanha the fat-capped rump cap next to it. Frequently sold and grilled side by side.
The same triangular tail of the bottom/top sirloin. Maminha is the Brazilian churrasco cut; tri-tip is the US (Santa Maria) name. Same muscle, different tradition.