Janis is a variant of Janice — a 20th-century American elaboration of Jane, from the Hebrew Yochanan ("God is gracious"). Janis Ian (born 1951) — American singer-songwriter; her 1975 song At Seventeen won the Grammy for Best Pop Vocal Performance and her Society's Child (1965), about an interracial relationship, was a teenage triumph.
Janis 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 Janis reduce to 8, The Visionary. This is a traditional interpretive system, not a factual claim about the name.