The Spanish word 'gas' comes from New Latin 'gas', which was actually coined by the 17th-century Flemish chemist Jan Baptist van Helmont. Van Helmont derived this term from the Latin word 'chaos', which in turn came from Ancient Greek 'χάος' (khaos), meaning 'chaos' or 'abyss'. Van Helmont chose this root because he viewed gas as a chaotic, formless substance, similar to the primordial chaos of Greek mythology. This scientific term has remained remarkably unchanged as it spread through various languages, maintaining its form in Spanish as 'gas'.

The Spanish word 'gas' is relatively unique and doesn't have many etymologically related words in Spanish, as it was a scientific term coined relatively recently. However, you might encounter 'caos' in Spanish, which comes from the same Greek root 'χάος' (khaos) and maintains the original meaning of 'chaos' or 'disorder'.

English speakers will find this word very familiar as 'gas' is identical in English and Spanish! Both languages borrowed it from the same scientific Latin source. Additionally, English words like 'chaos' and 'chaotic' are related, coming from the same Greek root 'χάος' (khaos) that inspired van Helmont to create the word 'gas'.