Aiko (愛子) is written with two kanji: ai (love) and ko (child) — meaning "loved child" or "beloved." The -ko suffix was traditionally used in many Japanese girls' names through the 20th century.
Princess Aiko of Japan (born 2001), daughter of Emperor Naruhito and Empress Masako, is the most prominent contemporary Aiko.
Aiko 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.
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In Pythagorean numerology the letters of Aiko reduce to 9, The Giver. This is a traditional interpretive system, not a factual claim about the name.