3:14 I AM WHO I AM.
This name for God points to His self-existence and eternality; it denotes “I am the One who is/will be,” which is decidedly the best and most contextually suitable option from a number of theories about its meaning and etymological source. The significance in relation to “God of your fathers” is immediately discernible: He’s the same God throughout the ages! The consonants from the Heb. word Yhwh, combined with the vowels from the divine name Adonai (Master or Lord), gave rise to the name “Jehovah” in English. Since the name Yahweh was considered so sacred that it should not be pronounced, the Massoretes inserted the vowels from Adonai to remind themselves to pronounce it when reading instead of saying Yahweh. Technically, this combination of consonants is known as the “tetragrammaton.”
MacArthur Study Bible note from Exodus 3:14