When we go from Greek further back to Hebrew, we also learn that e used to be…he (ה). Early Semitic writings didn’t have vowels (I talked about this during A), and he meant a rough aspirate (it was tough to find a source for rough aspirate but basically, it’s a sign for a noise we don’t have in English; think of how you’re supposed to say Hanukkah; that h noise is a rough aspirate). It became a letter in the Phoenician alphabet, but unsurprisingly, it represented the H sound.
It was the Greeks who started using he as their letter e—epsilon—for their short e sound (or adding an apostrophe when they did need the h sound—you’ll see more about this when I finally get to h). And because it was the Greeks, one of the most dominant, lasting cultures, other languages followed suit.
Omniglot, which has pages on Etruscan, Phoenician and Proto-Sinaitic (for better looks at the old versions of letters)