Theano (Θεανώ) is the Greek word for "divine" or "godly." Theano of Croton (6th c. BCE) was the wife and pupil of Pythagoras — herself a philosopher and mathematician who wrote treatises on virtue, piety, and the immortality of the soul.
She is one of the earliest known female philosophers in Greek tradition.
Theano 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 Theano reduce to 9, The Giver. This is a traditional interpretive system, not a factual claim about the name.