The name Lou is a diminutive form of the masculine given name Louis, which originated from the Old Frankish Chlodovech. This name was composed of the Germanic elements hlod, meaning "famous," and wig, meaning "combat" or "battle." The name Louis first appeared in the 7th century AD and was borne by several Frankish kings, including Louis I, also known as Louis the Pious, who reigned from 814 to 840 AD.

Lou gained popularity as a shortened form of Louis during the Middle Ages. One of the earliest recorded instances of the name Lou is found in the 13th-century French epic poem "The Song of Roland," where it is used as a nickname for the character Lohier. In the 14th century, the Italian poet Dante Alighieri mentioned the name Lou in his famous work "The Divine Comedy."

Throughout history, several notable figures have borne the name Lou. One of the most famous is Lou Gehrig, an American baseball player who played for the New York Yankees from 1923 to 1939. He was nicknamed "The Iron Horse" and is remembered for his incredible streak of 2,130 consecutive games played. Lou Gehrig was born in 1903 and passed away in 1941.

Another prominent Lou is Lou Reed, an American singer-songwriter, and musician who was a founding member of the influential rock band The Velvet Underground. He was born in 1942 and his solo career spanned several decades until his death in 2013. Lou Reed's music had a significant impact on the development of alternative and indie rock genres.

In the world of literature, Lou Andreas-Salomé was a Russian-born psychoanalyst and writer who was closely associated with the philosophers Friedrich Nietzsche and Sigmund Freud. She was born in 1861 and lived until 1937, leaving a lasting mark on the fields of philosophy and psychoanalysis.

Lou Costello, born in 1906 and died in 1959, was an American comedian and actor who formed the famous comedic duo Abbott and Costello with Bud Abbott. Their comedy routines, such as "Who's on First?," became iconic and influential in the world of comedy.

Another notable Lou is Lou Brock, an American professional baseball player who played for the St. Louis Cardinals and is considered one of the greatest base stealers in Major League Baseball history. He was born in 1939 and played until 1979, earning induction into the Baseball Hall of Fame in 1985.