While the ITCZ is a widely used term for the whole globe ( seasonally variable equatorial region where the Trade winds converge as part of the atmospheric Hadley cells circulation), the OTCZ is not as common, and I think it is mostly used in the Indian Ocean.

The ITCZ  solely refers to an atmospheric proccess (convergence and convection) while the OTCZ seems to refer to the ocean region where the ITCZ is enhanced. Therefore, the OTCZ does not refer to a convergence in the ocean circulation surface. On the contrary, the ITCZ drives a regional upwelling (divergence) in the ocean surface due to Ekman dynamics.