erc-keywords

erc-keywords is a variable defined in `erc-match.el'.
Its value is

nil

Documentation:
List of keywords to highlight in all incoming messages.
Each entry in the list is either a regexp, or a cons cell with the
regexp in the car and the face to use in the cdr. If no face is
specified, `erc-keyword-face' is used.

You can customize this variable.