/ˈmʌskjʊlətʃər/
[noun] The system of muscles in the body, or in a particular part of the body. It refers to how the muscles are arranged and how they work together as a whole.
The Latin word for 'muscle' literally meant 'little mouse' — ancient Romans thought a flexing bicep looked like a mouse running under the skin.
The story of 'musculature' begins with one of the most delightful observations in the history of language. Ancient Roman writers used the Latin word 'musculus' — which meant both 'little mouse' and 'muscle' — because they noticed that the movement of a muscle beneath the skin looked remarkably like a small mouse scurrying under a blanket. The word 'musculus' was itself a diminutive form of 'mus', meaning 'mouse', a root that also gave rise to the modern English word 'mouse' via Old English 'mūs'. This tiny creature gave its name to one of the most important systems of the human body.
From 'musculus', Latin developed the adjective 'muscularis', meaning 'relating to muscles', and later 'musculosus', meaning 'full of muscles' or 'muscular'. These forms passed into French as 'muscle' and 'musculaire', and by the 16th century, English had borrowed 'muscle' directly — most likely from Middle French 'muscle', which came straight from Latin 'musculus'. The word arrived in English writing around the 1520s, initially used in anatomical and medical contexts by scholars who were rediscovering classical texts.
The word 'musculature' itself is a later and more specialised formation. It appeared in English during the 19th century, borrowed from the French 'musculature', which had been constructed from Latin 'musculus' with the French suffix '-ature' (from Latin '-atura'), a suffix used to indicate a system or collective arrangement of something. So while 'muscle' refers to a single unit, 'musculature' refers to the entire organised network — the architecture of muscles working together. This kind of collective noun was especially useful to scientists, artists, and anatomists who needed to talk about the body in a systematic way.
The 19th century was a golden age for such technical vocabulary. As biology, physiology, and the fine arts all grew more sophisticated, writers and scientists needed precise words to describe complex systems. 'Musculature' filled a gap that 'muscle' alone could not fill. Sculptors and painters used the word to describe the arrangement of muscles in their models; physiologists used it to compare the muscle systems of different animals; doctors used it to discuss the physical condition of patients. The word carried a sense of completeness and structure that made it very useful across many fields.
It is worth noting that the 'mouse' connection does not stop with 'muscle'. The Proto-Indo-European root behind the Latin 'mus' is thought to be '*mūs-', and this ancient root spread remarkably far. It gave Greek 'mys' (meaning both 'mouse' and 'muscle'), which in turn produced the prefix 'myo-' used in modern medical terms like 'myocardium' (the muscle of the heart) and 'myalgia' (muscle pain). So whether you are talking about your biceps, a running rodent, or a cardiac condition, you are drawing on the same ancient observation made by people who watched bodies move thousands of years ago.