What is the program that suggests installable packages?
command-not-found is the package you are looking for.
Just as an addition to the previous answer:
To switch this off for your own account (without deinstalling the whole package and so disabling this for ALL users), you may just add the following line to your own ~/.bashrc:
unset command_not_found_handle
This reverts to the default bevaviour of bash (see /etc/bash.bashrc for the definition of the function command_not_found_handle: it calls command-not-found if it is installed, otherwise it prints the default "command not found" error message).