Origins
The English word "thunder" traces its origins deep into the Germanic branch of the Indo-European language family, with its earliest attestations found in Old English as "þunor," denoting both the atmospheric phenomenon of thunder and the name of the thunder-god Thor. This dual usage reflects a common ancient practice of personifying natural forces, where the deity and the natural event shared the same lexical identity. The Old English "þunor" itself derives from Proto-Germanic *þunraz, a term reconstructed to mean "thunder" or "the thunder-god," which is attested across various Germanic languages. For instance, Old Norse presents "Þórr," Old High German has "Donar," Old Saxon records "Thunaer," and Dutch preserves the cognate "donder," all referring to the thunder phenomenon or the associated deity.
The Proto-Germanic *þunraz is widely accepted as inherited from Proto-Indo-European (PIE), specifically from the root *(s)tenh₂-, which is reconstructed with the meaning "to thunder," "to resound loudly," or "to make a crashing sound." This PIE root is characterized by the presence of the laryngeal *h₂, which likely influenced the vowel coloring in descendant languages. The root *(s)tenh₂- is not directly attested but is inferred through comparative linguistic evidence, linking words related to loud sounds or thunderous noises across several Indo-European branches.
In the Italic branch, the same PIE root gave rise to Latin "tonāre," meaning "to thunder." This Latin verb is the source of several English derivatives, though these entered English through later borrowings rather than direct inheritance. For example, English "detonate," meaning "to thunder apart," derives from Latin "detonare," formed from "de-" plus "tonare." Similarly, "astonish" traces back to Vulgar Latin *extonāre, literally "to thunder at," which passed into Old French as "estoner" and then into English. The English word "stun" also derives from Old French "estoner," reflecting the semantic shift from the idea of being struck or overwhelmed as if by thunder. Additionally, the English "tone," originally referring to a sound or musical pitch, ultimately derives from Greek "tonos," meaning "stretching, tension," but its semantic field overlaps with the concept of sound, linking it conceptually to the notion of thunderous noise.