S: http://www.sciencemadesimple.co.uk/activities/thunder (last access: 30 June 2015); http://www.loc.gov/rr/scitech/mysteries/thunder.html (last access: 30 June 2015).
N: 1. mid-13c., from Old English þunor “thunder, thunderclap; the god Thor,” from Proto-Germanic thunraz, from PIE (s)tene- “to resound, thunder” (cognates: Sanskrit tanayitnuh “thundering,” Persian tundar “thunder,” Latin tonare “to thunder”). Swedish tordön is literally “Thor’s din.” The intrusive –d– also is found in Dutch and Icelandic versions of the word. Thunder-stick, imagined word used by primitive peoples for “gun,” attested from 1904.
2. A sharp or rumbling sound which accompanies lightning. It is emitted by rapidly expanding gases along the channel of a lightning discharge.
3. Thunder is the noise caused by the explosive expansion of air due to the heat generated by a lightning discharge. Thunder may have a sharp cracking sound when lightning is close by, compared to a rumbling noise produced by more distant strokes.
4. Cultural Interrelation: Related to Native American Mythology, we can mention the thunderbird, an enormous bird (according to many Northwestern tribes, large enough to carry a killer whale in its talons as an eagle carries a fish) who is responsible for the sound of thunder (and in some cases lightning as well).
We can mention as well the movie Thunderheart (1992) directed by Michael Apted.
S: 1. OED – http://www.etymonline.com/index.php?allowed_in_frame=0&search=thunder&searchmode=none (last access: 30 June 2015). 2. METEOTERM/IMV – http://wmo.multicorpora.net/MultiTransWeb/Web.mvc (last access: 30 June 2015). 3. TERMIUMPLUS. 4. http://www.native-languages.org/thunderbird.htm (last access: 2 July 2015); http://www.nytimes.com/movie/review?res=9E0CE3D9103AF930A35757C0A964958260 (last access: 3 July 2015).