Lennox is from the Scottish Gaelic Leamhnach — elm grove, an ancient earldom in Scotland. The name has surged in modern American naming alongside other Scottish -ox endings (Knox, Maddox, Fox).
Lennox 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 Lennox reduce to 3, The Communicator. This is a traditional interpretive system, not a factual claim about the name.