Janet is a medieval Scottish diminutive of Jane — itself the feminine of John, from the Hebrew Yochanan ("God is gracious").
Subject of Janet Jackson's documentary Janet (2022).
Janet 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 Janet reduce to 5, The Seeker. This is a traditional interpretive system, not a factual claim about the name.