Semele (Σεμέλη) is from the Phrygian zemelo (earth). Tricked by the jealous Hera into demanding to see Zeus in his true form, she was incinerated by his lightning — but Zeus rescued the unborn Dionysus from her ashes and sewed him into his thigh until birth.
Semele 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 Semele reduce to 5, The Seeker. This is a traditional interpretive system, not a factual claim about the name.