Why E-Risc?
Well the Risc part of the name is obvious, but why E. Well partly because its an Embedded processor intended to be embedded as a controller deep within a system or an ASIC. And partly as E comes logically before/below F. Where F is the freedom CPU. This is a desktop/workstation processor, to rival the latest x86 devices. So the E-Risc is somewhat more lowly...

Suggested naming conventions.
The E series of mythical CPUs even have a logical naming convention. They all start with E followed by the architecture revision (trailing zeros can be omitted) and completed by the base data width. E.g. the first generation 32 bit version will be called E1-32. This will hopefully avoid confusion as the architectures will evolve quickly (at the moment it is changing almost daily).