superstiĉo

Not super plus something. The word starts with the preposition super, which is a genuine Esperanto word meaning above, and a learner who cuts there is left holding stiĉo, which is not a word in this language at all. There is no stiĉ- root. Superstiĉo is one indivisible borrowing, and the test is the one the affix articles keep recommending: if the remainder after the cut is not itself a root, there was no cut.

And yet the seam was real once. Latin superstitio really is super plus stare, to stand: standing over, standing near. Which sense of standing over the Romans meant is argued about, and the likeliest reading is the posture of somebody hovering anxiously above a rite, doing it too much and too fearfully. Cicero used the word as an insult, against religio as the proper sort of observance. So this belongs with inspiri and maniko: the join you can see is real in the source language and dead in Esperanto, which is a much more interesting fact than a simple false friend.

Using it. Superstiĉa is the adjective, and it goes on people as well as beliefs: superstiĉa maristo, a superstitious sailor. Superstiĉulo is somebody given to them. The neighbours are magio, which is the craft; sorĉi, which is to work it; and kutimo, a habit, which is what most superstitions actually are once the belief has drained out of them.