Tendai is the Shona word for "give thanks" or "be grateful" — used as a unisex name across Zimbabwe.
Tendai Mtawarira (born 1985), the South African-born Zimbabwean rugby player who won the 2019 Rugby World Cup with the Springboks, is a notable bearer (the masculine usage).
Tendai 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 Tendai reduce to 8, The Visionary. This is a traditional interpretive system, not a factual claim about the name.