[Maria-developers] Reserved words

How can one find a definitive list of reserved words for a particular version? The comments in sql/lex.h say that that's a list of all reserved words and functions, but it appears to contain some words that are neither (such as ACTION). SELECT * FROM mysql.help_keyword also lists ACTION ACTION is listed in the MYSQL docs as an example of one of the keywords that MySQL permits "because many people previously used them"