Concordia is from the Latin concordia (harmony, agreement). Concordia is the Roman goddess of harmony and civic unity — equivalent to Greek Harmonia. The Temple of Concordia in the Roman Forum (rebuilt 367 BCE) and the Temple of Concordia at Agrigento (Sicily, UNESCO World Heritage) are works of classical architecture. Appears in Ovid's Fasti and Cicero's political works.
Concordia 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.
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In Pythagorean numerology the letters of Concordia reduce to 1, The Leader. This is a traditional interpretive system, not a factual claim about the name.