1
general::
Make or cause someone to make a mistake, as in The other finalist tripped up when he was asked to spell "trireme," or They tripped him up with that difficult question. [Second half of 1700s]
American Heritage Idioms
2
general::
Phrase(s): trip someone up
1. Lit. to cause someone to trip; to entangle someone’s feet. (Someone includes oneself.) • The rope strewn about the deck tripped him up. • The lines tripped up the crew. 2. Fig. to cause someone to falter while speaking, thinking, etc. • Mary came in while the speaker was talking and the distraction tripped him up. • The noise in the audience tripped up the speaker.
McGrawhill's American Idioms And Phrasal Verbs