Wikipedia
OTcl
OTcl usually refers to an object oriented extension of Tcl created by David Wetherall at MIT. It is used in network simulator (NS-2) and usually run under Unix environment. This was later extended into XOTcl.
OTcl may also refer to the unrelated IXI Object Tcl extension by Dean Sheenan.
These object Tcl extensions predate the more popular incr Tcl.