Kayla has two parallel origins. As a Yiddish/Hebrew name, it derives from Keila — possibly meaning "crown" or "laurel." As a modern English coining, it combines Kay (Greek "rejoice" or English short of Katherine "pure") with the popular -la ending.
It peaked at #11 in 1990. Today Kayla sits in the U.S. top 300.
Kayla 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 Kayla reduce to 5, The Seeker. This is a traditional interpretive system, not a factual claim about the name.