In a well-known passage, Treebeard explains to Merry and Pippin the Entish philosophy of naming:
For I am not going to tell you my name, not yet at any rate.’ A queer half-knowing, half-humorous look came with a green flicker into his eyes. ‘For one thing it would take a long while: my name is growing all the time, and I’ve lived a very long, long time; so my name is like a story. Real names tell you the story of the things they belong to in my language, in the Old Entish as you might say. It is a lovely language, but it takes a very long time to say anything in it, because we do not say anything in it, unless it is worth taking a long time to say, and to listen to.
In other words, the name of a thing is its narrative: things are identified by their temporal eventfulness. According to Robert Jenson (Systematic Theology, Vol. 1: The Triune God), what is true of Treebeard is likewise true of the God of the Old and New Testaments.
God… is uniquely described by the narrative of the Exodus-event, and the one so described has a personal proper name, JHWH. The description and the name in their interplay determine Israel’s relationship to her God. Asked who God is, Israel’s answer is, “Whoever rescued us from Egypt.” Asked about her access to this God, Israel’s answer is, “We are permitted to call on him by name”… In [the Decalogue], the name and the narrative description are side by side, to make one identification: “I am JHWH your God, who brought you out of the Land of Egypt.”…
To the question “Who is God?” the New Testament has one new descriptively identifying answer: “Whoever raised Jesus from the dead.” Identification by the Resurrection neither replaces nor is simply added to identification by the Exodus; the new identifying description verifies its paradigmatic predecessor…. Thus the phrase “Father, Son, and Holy Spirit” is simultaneously a very compressed telling of the total narrative by which Scripture identifies God and a personal name for the God so specified; in it, name and narrative description only appear together, as at the beginning of the Ten Commandments, but are identical.
In Treebeard’s terms, accordingly, Yahweh’s name is a “real name” first, because it “tells you the story of the thing” it names, and secondly, because like any other living thing, it is “growing all the time.”