The Spanish word 'puño' meaning 'fist' comes directly from the Latin word 'pugnus', which had the same meaning. This is a straightforward inheritance where both the form and meaning have remained remarkably stable over time, with just the typical sound changes that occurred as Latin evolved into Spanish.

Some related Spanish words include 'puñetazo' (punch), 'puñado' (handful), and 'empuñar' (to grasp). All these words build on 'puño' to describe actions or quantities related to what you can do with or hold in a fist.

While English 'fist' comes from Germanic roots, we do have some English words related to Latin 'pugnus', such as 'pugilism' (the art of boxing), 'pugilist' (a boxer), and 'pugnacius' (eager to fight, combative). These words all connect to the fighting aspect associated with using one's fists.