Think of the Jewish legends of the Golem. See
http://en.wikipedia.org/wiki/Golem which provides an excellent summary if you aren′t otherwise very familiar with them. My point is that a Golem, an image of some kind, is brought to life by attaching a piece of paper on which is written one of the names of God to the Golem′s mouth or forehead.
Here the idea is that a name of God is sufficiently powerful in itself that even writing it on a piece of paper is sufficient to animate something that is inanimate.
In a common variant the living Golem has the Hebrew word אמת (
’emeθ, ‘truth’) engraved on its forehead and can be returned to non-living form by merely scraping off the letter א leaving the Hebrew word מת (
mēθ, ‘dead’) now engraved on its forehead.
In such tales merely the writing of a word creates the magic (although one may well imagine other conjurations that must be performed). In the case of Sauron’s ring it also appears that simply engraving the couplet may not be the whole magic, but that it is part of it. Possibly merely removing the inscription from the Ring would have been sufficient to break its power, but Gandalf does not indicate that he knows any way to accomplish this. Only the fires of Mount Doom are powerful enough to alter the Ring and finally destroy it.