Certain words such as SELECT, DELETE, or UPDATE are reserved and should not be used for identifiers such as table, feature class and column names. Attempting to use a reserved word as a table name will return an error that the table (or feature class) name is invalid. Using a reserved word as a column name will return an error indicating that the column name is invalid. Copy/Paste from a data source where the word is not reserved will add a "_" to the end of any table or column name that is reserved within the file geodatabase.
Reserved words within a file geodatabase: