παχύς

Etymology: From Ancient Greek παχύς (pakhús). Shares Proto-Indo-European roots with Latin 'pinguis' (fat). The concept of thickness or density is fundamental to this word's meaning, which has remained remarkably stable since ancient times. Understanding its connection to words like 'pachycephalosaurus' (thick-headed dinosaur) and 'pachyderm' (thick-skinned animal) can help remember its meaning.