Wiktionary
n. 1 Any word that has a magical effect when uttered. 2 (context in teaching polite expressions to children English) mnemonic of the word (term: please) or (term: thanks).
Wikipedia
Magic words are words which have a specific, and sometimes unintended, effect. They are often nonsense phrases used in fantasy fiction or by stage prestidigitators. Certain comic book heroes use magic words to activate their super powers. Magic words are also used as Easter eggs or cheats in computer games, other software, and operating systems. (For example, the words xyzzy, plugh, and plover were magic words in the classic computer adventure game Colossal Cave Adventure).
Usage examples of "magic word".
Perhaps there was a magic word to open it but I did not have the word.
Now he is the Ali corn, and he says he has associated with human beings as long as human beings have existed-maybe longen That is, with those who know the magic word to tame him tem porarily.