What the meaning of name Jackie Lou?

Jackie is a masculine and feminine diminutive of both Jack and Jacqueline.

Jack is derived from the Medieval diminutive of John-- Jackin and Jankin.

John is the English form of the Latin Iohannes, which comes from the Greek Ioannes; ultimately originating from the Hebrew name Yochanan, meaning "Yahweh is Gracious."

Jacqueline is the French (and English) feminine form of Jacques, which is the French form of both Jacob and James.

When boiled down, Jacob means either "Supplanter" or "May God Protect."

James was born from Jacob.

As for Lou... it is a shortened nickname of LouisLouise.

Louis is the French version of Ludovicus, the Latinized form of Ludwig, which is from the Germanic name Chlodovech; meaning "Famous Warrior."

Louise means the same, as it is the French, English, and Dutch feminine form of Louis.