Millicent is the English form of the Old Germanic Amalswind — amal ("work, vigor") + swind ("strong"). Millicent Patrick (1915-1998) — American makeup artist; designed the Creature from Creature from the Black Lagoon (1954) — making her one of the first women to design a major Hollywood monster; her credit was suppressed by jealous makeup-department head Bud Westmore; the 2019 book The Lady from the Black Lagoon recovered her legacy.
Millicent 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 Millicent reduce to 7, The Seeker. This is a traditional interpretive system, not a factual claim about the name.