Sayo is from the Yoruba Sayọ̀ — s- turned into + ayọ̀ (joy) — joy has turned into / has become joy. Sayo is one of the Yoruba feminine + unisex names — central to traditional Yoruba theophoric + life-statement naming heritage.
Sayo 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 Sayo reduce to 6, The Nurturer. This is a traditional interpretive system, not a factual claim about the name.