The verb “to alarm” signifies, in Freemasonry, to give notice of the approach of someone desiring admission. Thus, to alarm the Lodge is to inform the Lodge that there is someone without who is seeking entrance.

As a noun, the word “alarm” has two significations:

1. 1. An alarm is a warning given by the Tiler, or other appropriate officer, by which he seeks to communicate with the interior of the Lodge or Chapter.

  In this sense, the expression so often used, "an alarm at the door," simply signifies that the officer outside has given notice of his desire to communicate with the Lodge.

1. 2. An alarm is also the peculiar mode in which this notice is to be given. In modern Masonic works, the number of knocks given in an alarm is generally expressed by musical notes. Thus, three distinct knocks would be designated thus, . . .; two rapid and two slow ones thus, . . . - - and three knocks, three times repeated thus, . . ./. . . /. . . , etc.

The word comes from the French *alarme*, which in turn comes from the Italian *all'arme*, literally a cry to arms, uttered by sentinels surprised by the enemy. The legal meaning of to alarm is not to frighten, but to make one aware of the necessity of defense or protection.

This is precisely the Masonic signification of the world.