Madigan is from the Irish Ó Madagáin — descendant of the little dog (from madra meaning dog). Madigan Men (CBS 2000) — short-lived American sitcom. Cathy Madigan — Irish-American actress. Princess Madigan — The Princess Bride-influenced naming. General Madigan — multiple US Army historical figures. Madigan appears as a character name in modern American fiction including works by Lee Smith and Pat Conroy.
Madigan 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 Madigan reduce to 4, The Builder. This is a traditional interpretive system, not a factual claim about the name.