Cynthia is from the Greek Kynthia — "woman of Mount Cynthus," the mountain on Delos where Artemis was born. An epithet of Artemis, the Greek moon-goddess, used by Roman poets including Propertius for his beloved. A top-10 US baby name from 1957 to 1963, peaking at #7 in 1958 and 1959. Cynthia Nixon (born 1966) — American actress and politician; played Miranda in Sex and the City; 2018 NY gubernatorial candidate. Cynthia Erivo (born 1987) — British actress; Tony, Grammy, Emmy winner; one Oscar nomination away from EGOT.
Featured in Propertius's Elegies (the poet's beloved was Cynthia).
In Pythagorean numerology the letters of Cynthia reduce to 8, The Visionary. This is a traditional interpretive system, not a factual claim about the name.