Anežka is the Czech form of Agnes — from the Greek hagne, meaning "pure." Saint Anežka of Bohemia (1211-1282) was the Czech princess who founded the first hospital in Prague, canonized in 1989.
Anežka is widely used in the Czech Republic.
Anežka 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 Anežka reduce to 3, The Communicator. This is a traditional interpretive system, not a factual claim about the name.