Leontion (Λεόντιον) was the Athenian Epicurean philosopher of the late 4th c. BCE — a student of Epicurus himself who wrote a famous (now lost) treatise refuting the philosophy of Theophrastus, head of the Lyceum.
Featured in Diogenes Laërtius's Lives of Eminent Philosophers.
Leontion 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 Leontion reduce to 5, The Seeker. This is a traditional interpretive system, not a factual claim about the name.