eldoc-message-commands-table-size is a variable defined in `eldoc.el'.
Its value is

Used by `eldoc-add-command' to initialize `eldoc-message-commands' obarray.
It should probably never be necessary to do so, but if you
choose to increase the number of buckets, you must do so before loading
this file since the obarray is initialized at load time.
Remember to keep it a prime number to improve hash performance.