I think that comes from the ideas behind vector decomposition (remember physics 101? ;-)). When you decompose a goal into several linearly independent sub-goal

I think that comes from the ideas behind vector decomposition (remember physics 101? ;-)). When you decompose a goal into several linearly independent sub-goals - those sub-goals are said to be 'orthogonal' since they don't have any interaction/interdependence with one another.