Pax is from the Latin pax (peace) — the personification of peace in Roman mythology (the equivalent of the Greek Eirene). Pax in classical art — Roman Pax appears on coins, statues, and friezes throughout the Roman imperial period; her iconography (caduceus, olive branch, cornucopia) influenced Western depictions of peace for 2,000+ years. Princess Pax — modern celebrity-naming examples.
Pax 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 Pax reduce to 5, The Seeker. This is a traditional interpretive system, not a factual claim about the name.