Tully is from the Irish Ó Taithligh — descendant of the peaceful one; also an Anglicized form of Tullius (the Roman nomen of Cicero — Marcus Tullius Cicero). Tully (the historic English name for Cicero) — Marcus Tullius Cicero (106-43 BCE) — the Roman statesman, philosopher, and orator; one of the most-influential figures in Roman history; in medieval and Renaissance England, Cicero was widely referred to as "Tully" — appearing in Shakespeare, Marlowe, and most English literature through the 18th century; the works of Tully shaped Western rhetoric, Stoic philosophy, and Christian humanism. Sturgis Tully — modern American figure.
Tully 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 Tully reduce to 9, The Giver. This is a traditional interpretive system, not a factual claim about the name.