Euphrosyne (Εὐφροσύνη) is one of the three Charites (Graces) in Greek mythology — the goddess of mirth, joy, and good cheer. From eu (good) and phrēn (mind, spirit).
Euphrosyne is rare as a given name but powerful.
Euphrosyne 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 Euphrosyne reduce to 2, The Peacemaker. This is a traditional interpretive system, not a factual claim about the name.