tropezar
stumble
trope
to turn
+
zar
tsar (Russian emperor)
Tropezar means to stumble. Imagine a zar1 (tsar) who turns0 (trope0) and stumbles, creating a memorable image for tropezar.
verb
  1. stumble
    To stumble or trip over something
    Tropecé con una piedra en el camino. // I stumbled on a stone on the path.