Guillaume,
You are correct, there are no stupid questions. You are also correct about the use of the word pass meaning the same as checking or possibly even folding. The game has evolved and one of the changes, is the use and meaning of the word "pass." In a draw game, like " Jacks or better" each player in turn would respond by either opening the betting (they would later have to prove that they had openers), or "pass" which meant that they did not have the qualifying hand or "openers." A player rapping the table, or saying I pass, or pass, or any gesture that indicated they did not want to wager was the same as a check. They were still allowed to compete if another player opened.
In a stud game, a player facing a bet may "pass' or "fold" by turning their face up cards over. They are out. The hand is dead. There used to be games that were "bet-or-out," or "pass-and-out," or "forced bet" games so...when the action came to you, you either had to bet, raise a bet in front of you, or fold, there was no other option. If you were first to act you had to Pass (fold), or bet.
The confusion is partly in the english lanquage, there are many words that have similar meanings. Pass/Check, Pass/Fold are kind of the same but it depends on the game of poker being played.
I will give you the definition of the word PASS from Chuck Ferry's Rules Of Poker Book; 1) Decline to bet. In a pass-and-out game, this differs from a check, because a player who passes must fold ....2) Decline to call a wager, at this point you must discard your hand and have no further interest in the pot.
Rapping the table or some other gesture is generally accepted as checking but remember, checking and passing can have different meanings depending on the game being played. Your original question would still require the player to surrender his hand before it is considered dead. Tapping the table, or rapping on the table, when facing a bet (especially head to head), is not enough to kill the hand.
I hope this helps.