Letters after the last example WSJ Crossword Clue

Think of what you might write when you're tired of listing every single item.

??? is an abbreviation for 'et cetera,' meaning 'and other similar things' or 'and so forth.'

The clue refers to the abbreviation '???,' which stands for 'et cetera,' meaning 'and other similar things' or 'and so forth.' It's often used at the end of a list to indicate that more examples exist but are not listed.

And more like that: Abbr., “The list goes on and on”, Common Latin abbreviations are a.m., i.e., e.g., ___, Multipurpose shortening?, "And other stuff like that": Abbr.