Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
show up (v.)
The two most commonly encountered senses, the intransitive “to appear” (He hasn’t shown [showed] up yet) and the transitive “to expose” or “to reveal” (The little man’s challenge showed up the bully for the coward he was), are appropriate in all but the most Formal and Oratorical English.
