MERRIAM-WEBSTER Main Entry: booby trap Pronunciation Guide Function: noun Etymology: 1booby 1 : a trap for the unwary or unsuspecting: a : a trap laid to play a trick on an unwary person <booby traps with buckets of water suspended over doors -- Robert Graves> b : a concealed explosive device usually attached to some harmless-looking object <the booby trap exploded when he touched the doorknob> c : an object wired to set off an explosion when touched <the car, which they suspected might be a booby trap -- Combined Operations> 2 : a critical or potentially dangerous aspect (as of a problem or situation) : PITFALL <words and expressions which are booby traps when used in the other language -- Richard Joseph>
The usual meaning of "boobytrap" is military. The purpose is to kill or maim the enemy. In many ways, it is better to injure the enemy than kill him. If he is killed, he is replaced. End of problem. But he is seriously injured, he requires medical care, food, transportation, housing, etc. The injured soldier requires attention for days, perhaps years.
For "pegadinha", I'd suggest prank or practical joke. The pegadinhas I used to watch on Rede were not practical and they certainly were not jokes. They showed cruelty and callousness, and many people suffered because of them.