 The term had been in use since the end of the seventeenth century.Furthermore, "The India Directory"  in its entry for Fernando de Noronha, an island off the coast of Brazil, mentions it had been visited frequently by ships "occasioned by the currents having horsed them to the westward".Heating of the earth near the equator leads to large amounts of convection along the monsoon trough or Intertropical convergence zone.