Mahalia comes from the Hebrew Mahalath (מָחֲלַת), meaning "tender one" or possibly from a root meaning "sickness/affliction" later reinterpreted as "affectionate." In Genesis, Mahalath is a daughter of Ishmael and one of Esau's wives.
King's "I Have a Dream" speech — it was Mahalia who called out "Tell them about the dream, Martin!" that prompted the famous improvisation.
Mahalia 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 Mahalia reduce to 9, The Giver. This is a traditional interpretive system, not a factual claim about the name.