If something perplexes you, it confuses and worries you because you do not understand it or because it causes you difficulty. It perplexed him because he was tackling it the wrong way. if something perplexes you, it makes you feel confused and worried because it is difficult to understand = puzzle (perplex (14-17 centuries), from perplexus, from plexus )
[ p&r-'pleks ] (transitive verb.) 1593. obsolete perplex, adjective, involved, perplexed, from Latin perplexus, from per- thoroughly + plexus involved, from past participle of plectere to braid, twine; more at PER-, PLY.