Echo (Ἠχώ) is the Greek word for "sound" or "reverberation." The Oread nymph cursed by Hera to repeat only the last words spoken to her — punishment for distracting Hera with chatter while Zeus consorted with other nymphs. She fell in unrequited love with the beautiful Narcissus, who rejected her; she pined away until only her voice remained. From her name the modern English word "echo."
Featured in Ovid's Metamorphoses (Book 3).
Echo does not currently appear in the US Social Security Administration's top 1,000 girls' names, so we don't publish a US rank or birth count for it. That says nothing about the name's standing elsewhere in the world — only that it sits outside the ranked US data we rely on.
In Pythagorean numerology the letters of Echo reduce to 4, The Builder. This is a traditional interpretive system, not a factual claim about the name.