Who coined the name 'Earth Day' for the 1970 event?

Julian Koenig coined the name “Earth Day” for the 1970 event.

Koenig was an advertising executive who served on the organizing committee for the first nationwide environmental teach-in. He noticed that the planned date, April 22, shared a rhyme with his birthday and proposed “Earth Day” as a memorable name. The phrase appeared in promotional material and quickly caught public attention.

The event had initially been described with names such as “National Environment Teach-In.” Senator Gaylord Nelson conceived the campaign, Denis Hayes became its national coordinator, and many organizers still used “teach-in” language during the planning stage. Koenig’s shorter name proved easier for newspapers, participants, and the public to adopt.

This is why Denis Hayes is sometimes mistakenly credited: he organized the national campaign and helped turn the idea into a massive event. Nelson was its principal political originator, but the name itself is generally credited to Koenig. On April 22, 1970, an estimated 20 million Americans participated.