A Part that serves as an anchor point for both Platter Bearing Housing and Tonearm, as well as having the TT's controls mounted on it, is OK to be referred to as a Chassis.
A Chassis can be found to be mounted on a Exotic Design as a Plinth, a Basic Design as a Plinth and on some alternate designs no Plinth is used, Tinned Vegetables have been used as the Supporting Mount.
A Plate in the form of Metal, Wood or Plastics solely used to support the Platter Spindle Housing, Motor and Tonearm is OK to be referred to as a Chassis or Plinth.
Some Designs come with a dedicated Sub-Plate produced from similar or identical material to the Chassis or Plinth. The additional Sub-Plate is OK to be referred to as a Sub-Plinth or even a Sub Sub-Plinth depending on the tiers in place for the assembly.
Tomatoes being pronounced as Tomartoes - Tomaytoes seems to be the description being questioned.