thunder

Thunder comes from Old English þunor, tracing back through Proto-West Germanic *þunr to Proto-Germanic *þunraz, and ultimately to the Proto-Indo-European root *(s)ten-, meaning 'to thunder.'

The word has stayed close to its sound-making root throughout its history, moving from Old English þunor and þunrian (the verb 'to thunder') into the Middle English forms thonder and thundren, settling into the modern noun and verb we use today.

It's a doublet of Thunor and Thor, both descending from the same Germanic root — meaning the storm god's name and the sound of a storm share the exact same ancestry. It's also distantly related to English words like astound, astonish, and stun, which trace to the same Proto-Indo-European root.