The Spanish word 'ciempiés' (meaning 'centipede') comes from combining two Latin words: 'centum' meaning 'hundred' and 'pedes' meaning 'feet'. This is a compound word that literally translates to 'hundred feet', describing the many pairs of legs that characterize these arthropods. The Latin 'centum' evolved into Spanish 'cien', while Latin 'pedes' became Spanish 'pies', and these combined to form 'ciempiés'.

The transformation from 'centum' to 'cien' and 'pedes' to 'pies' follows regular sound changes that occurred as Latin evolved into Spanish. When these words combined, the 'n' from 'cien' was modified to 'm' before the 'p' of 'pies', which is a common phonetic change in Spanish (and many other languages) where 'n' becomes 'm' before labial consonants like 'p'.

Two common Spanish words that are directly related to 'ciempiés' are its component parts: 'cien' (meaning 'hundred') and 'pies' (meaning 'feet'). These are both very frequent words in Spanish that beginners learn early. 'Cien' is used in counting and mathematics, while 'pie' (singular of 'pies') is used for both human feet and as a unit of measurement, just like in English.

The English word 'centipede' is a perfect cognate to Spanish 'ciempiés', as it comes from the same Latin roots. The English version maintains spelling closer to the original Latin 'centum' in its first part 'centi-'. English also has many other words using this 'cent-' root to mean 'hundred', such as 'century', 'percent', and 'cent' (the coin, being one-hundredth of a dollar). Similarly, the '-pede' part is related to many English words referring to feet, such as 'pedestrian', 'pedal', and 'podiatrist'.