The word 极其 is formed through the combination of two classical Chinese elements: 极, meaning "extreme" or "utmost", and 其, a classical function word often used to add emphasis or refer back to a subject. They merge to create a single, fused adverb where 其 intensifies the inherent extremity of 极, resulting in a term that means "extremely" or "exceedingly". This formation exemplifies a common pattern in Chinese where an abstract core concept is reinforced by a grammatical particle to solidify its adverbial function and amplify its meaning.