Liisi is the Estonian/Finnish diminutive of Elisabeth — from the Hebrew Elīsheva (my God is my oath). Liisi Lass — Estonian artist. Liisi Eesmaa — modern Estonian figure. Liisi Oja — Estonian academic. Liisi Kaibald — modern Estonian-American figure. Princess Liisi — Estonian heritage naming.
Liisi 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 Liisi reduce to 4, The Builder. This is a traditional interpretive system, not a factual claim about the name.