The name Lenny is a diminutive form of the given name Leonard, which has its origins in the Germanic languages. Leonard is derived from the elements "leun" meaning "lion" and "hart" meaning "brave" or "hardy." Together, the name can be interpreted to mean "brave as a lion" or "lion-hearted."

The name Leonard gained popularity during the Middle Ages, particularly in regions with Germanic influence, such as present-day Germany, Austria, and parts of France. It was often associated with strength, courage, and bravery, qualities admired in medieval times.

One of the earliest recorded instances of the name Leonard can be found in the 5th century, when a Frankish noble named Leonard of Noblac lived in what is now western France. He later became venerated as a saint in the Catholic Church, and his cult following contributed to the widespread use of the name across Europe.

During the medieval period, several notable figures bore the name Leonard. One example is Leonard of Pisa, an Italian mathematician and philosopher who lived in the 13th century and made significant contributions to the development of algebra.

In the Renaissance era, the name Leonard continued to be used, and several artists and intellectuals carried it. Leonard da Vinci (1452-1519), the famous Italian polymath, is perhaps the most renowned bearer of the name from this period.

Other notable individuals with the name Leonard include the Russian composer Leonard Bernstein (1918-1990), known for his works such as "West Side Story" and his contributions to classical music and conducting.

Leonard Cohen (1934-2016) was a Canadian singer-songwriter and poet, whose introspective and poetic lyrics earned him critical acclaim and a devoted following.

In the realm of literature, Leonard Woolf (1880-1969) was a British writer and publisher, best known as the husband of the renowned author Virginia Woolf.

Leonard Nimoy (1931-2015) was an American actor and director, who gained worldwide fame for his portrayal of the iconic character Spock in the "Star Trek" television series and films.

The diminutive form Lenny emerged as a familiar or affectionate version of the name Leonard, particularly in English-speaking countries. While the origins of the name can be traced back to the Germanic languages and medieval Europe, its diminutive form Lenny has become a distinct and widely recognized name in its own right.