nmsPibToMib is the root of the nms-assigned OID subtree for MIBs which are algorithmically generated/translated from nms PIBs with OIDs assigned under the nmsPIB subtree. These generated MIBs allow management entities (other the current Policy Server) to read the downloaded policy. By convention, for PIB 'nmsPIB.x', the generated MIB shall have the name 'nmsPibToMib.x'.
Sources for this description
Multiple manufacturers; see the original MIB MIB copies (LibreNMS/Observium Community)