The Spanish verb 'rellenar' (meaning 'to fill again' or 'to refill') is formed from three main components: the prefix 're-' meaning 'again', the root 'lleno' meaning 'full', and the verbal suffix '-ar'. The root 'lleno' comes from Latin 'plenus' meaning 'full' or 'complete'. When these elements combined, they created a verb that literally means 'to make full again'.

A simpler and very common Spanish word from the same root is 'lleno' (meaning 'full'). This adjective is used frequently in everyday Spanish and is directly related to 'rellenar'. You might hear 'está lleno' (it's full) or 'lleno de gente' (full of people). Understanding this connection can help you remember that 'rellenar' is essentially about making something 'lleno' (full) again.

Several English words share the same Latin ancestor 'plenus'. The most obvious ones are 'plenty' and 'plentiful', both referring to having a full or abundant amount of something. We can also see this root in words like 'replenish' (to fill again - notice how this has the same basic meaning as 'rellenar'!) and 'complete' (literally meaning 'thoroughly filled'). Even the word 'plenty' carries the basic idea of 'fullness' that we see in the Spanish 'rellenar'.