Definition of muscular

The word "muscular" originates from the Latin root word "musculus," which means "little mouse." This might seem like a strange origin for a word related to strength and power, but it makes sense when you consider that ancient anatomists mistakenly believed that tiny mouse-like creatures called musculi lived inside our muscles, helping them to move. In fact, the Greek physician Galen (AD 130–200) famously proposed that small animals called myrmekes ("ants") lived inside our muscles and initiated contractions. These mythical "muscle creatures" were believed to be the reason that muscles trembled and twitched. It wasn't until the 17th century that British anatomist Thomas Willis debunked these myths and explained that muscles actually contracted due to the actions of other structures called tendons. Over time, the term "muscular" came to describe animals with well-developed muscles, such as lions and horses, as opposed to more slender creatures like deer. Eventually, the word came to mean anything that is strong, powerful, and full of muscle mass, including athletes, football teams, and even cars and planes. So next time you admire a particularly "muscular" person or animal, remember the tiny "mouse-like creatures" that inspired the term!