== 名前と語源 ==
原ケルト語では *''Toranos''('Thunder')と呼ばれ、これは原インド・ヨーロッパ語(PIE)の「雷」の語幹 *''(s)tenh₂-''から派生した *''Tonaros''のメタテーゼ(音の切り替え)により派生したものと推定されている。この名前の原型は、クルニア(Clunia、現在のブルゴス県)のローマ軍将校が奉納した祭壇に見られるtanaro(チェスター、AD154)というダブスタ形式と、ポー川(北イタリア)の古名であるガリア語のハイドロニム Tanarus(「雷鳴」または「激しい」)で証明されている<ref name=":0">Matasović, Ranko, https://books.google.com/books?id=YN_YPQAACAAJ, Etymological Dictionary of Proto-Celtic, 2009, Brill, isbn:9789004173361, pages384</ref><ref>Koch, 2020, pp142–144</ref><ref>Sutrop, Urmas. "Taarapita-the Great God of the Oeselians". In: ''Folklore: Electronic Journal of Folklore'' 26 (2004). p. 40</ref>。また、ヨーロッパの同種のヒドロニウムも同じルーツに属すると提唱されている<ref>Pedreño, Juan Carlos Olivares. "Los dioses soberanos y los ríos en la religión indígena de la Hispania indoeuropea". In: ''Gerión'' n. 18 (2000). p. 204. ISSN:0213-0181</ref>。PIEのs-initialは、ケルトベリアのsteniontes、stenion、stenaに残っているようである<ref>Koch, 2020, pp142–144</ref>。
The [[Proto-Celtic]] form of the name is reconstructed as *''Toranos'' ('Thunder'), which derives through [[Metathesis (linguistics)|metathesis]] (switch of sounds) from an earlier *''Tonaros'', itself from the [[Proto-Indo-European language|Proto-Indo-European]] (PIE) stem for 'thunder', *''(s)tenh₂-''. The original, unmetathesized form of the name is attested in the dative form ''tanaro'' ([[Chester]], 154 AD), found on a votive altar dedicated by a Roman officer from [[Clunia]] (modern [[Province of Burgos|Burgos Province]]), and in the Gaulish [[hydronym]] ''[[Tanaro (river)|Tanarus]]'' ('thundering' or 'thunderous'), an ancient name of the [[River Po]] (northern Italy). Similar European hydronyms have also been proposed to belong to the same root. The PIE ''s''-initial seems to have been retained in [[Celtiberian language|Celtiberian]] ''steniontes'', ''stenion'', and ''stena''.{{sfn|Koch|2020|pp=142–144}}
In the [[Indo-European languages|Indo-European]] context, the Proto-Celtic name *''Tonaros'' is identical to the [[Proto-Germanic]] Thunder-god ''*Þun(a)raz'' (cf. [[Old Norse|ON]] [[Thor|''Þórr'']], [[Old English|OE]] ''Þunor'', [[Old Saxon|OS]] ''Thunar'', [[Old Frisian|OFris.]] ''Thuner'', [[Old High German|OHG]] ''Donar''), and further related to the [[Vedic Sanskrit|Sanskrit]] ''stánati'' and [[Latin]] ''tono'', both meaning 'to thunder'''.''<ref name=":0" /><ref name=":1">{{Cite book|last=Delamarre|first=Xavier|url=https://books.google.com/books?id=C3BKPgAACAAJ|title=Dictionnaire de la langue gauloise: Une approche linguistique du vieux-celtique continental|date=2008|publisher=Errance|isbn=9782877723695|pages=290|language=fr}}</ref> According to scholar Peter Jackson, the Celtic–Germanic [[isogloss]] *''Þun(a)raz'' ''~ *Tonaros'' may have emerged as the result of the fossilization of an original epithet (or [[epiclesis]]) of the [[Proto-Indo-European]] thunder-god *''[[Perkwunos|Perk<sup>w</sup>unos]]''.<ref>{{Cite journal|last=Jackson|first=Peter|date=2002|title=Light from Distant Asterisks. Towards a Description of the Indo-European Religious Heritage|journal=Numen|volume=49|issue=1|pages=61–102|doi=10.1163/15685270252772777|issn=0029-5973|jstor=3270472}}</ref>