ガリア語では、Cernunnosの名前の語源は、「角」「鹿の角」を意味するkarnonである。 Karnonはラテン語の''cornu''やゲルマン語の''*hurnaz''と同族で、最終的にはプロト・インド・ヨーロッパ語の''*k̑r̥no-''に由来する<ref>Pokorny (1959) "k̑er-, k̑erə-; k̑rā-, k̑erei-, k̑ereu"[http://www.utexas.edu/cola/centers/lrc/ielex/X/P0929.html], https://web.archive.org/web/20140307155522/http://www.utexas.edu/cola/centers/lrc/ielex/X/P0929.html, 2014-03-07 </ref>。大陸ケルト語のガリア人とガラテヤ人の支流には、「角」(''karn-'' "horn")という語源が見られる。アレキサンドリアのヘシキウス(Hesychius)は、ガラテヤ語のkarnon (κάρνον) を「ガリアのラッパ」、つまりテサロニカのエウスタティウス(Eustathius)がcarnix (κάρνυξ) として挙げたケルト軍の角笛を、動物の形の鐘を持つ楽器と解釈している<ref>Delamarre; Greek text and English translation of the passage from Eustathius' Homeric commentaries given by Edward Wigan, "Account of a Collection of Roman Gold Coins", ''Numismatic Chronicle'' 5 (1865), p. 11 [https://books.google.com/books?id=0VwUAAAAYAAJ&pg=PA11&dq=carnyx+Eustathius&hl=en&ei=yEPDTMPmA4SfnAf__a3UCQ&sa=X&oi=book_result&ct=result&resnum=2&ved=0CCsQ6AEwAQ#v=onepage&q=carnyx%20Eustathius&f=false online.]</ref>。この語源はケルトの諸集団の名前にも現れ、中でも「角のある者」という意味のCarnutesが有名である<ref>Also ''Carni'' and ''Carnonacae''.</ref>。また、碑文に見られるいくつかの人名にも見られる<ref>Such as ''Carnarus'', ''Carnatus'', ''Carneolus'', ''Carnius'', and ''Carnicus''. Altay Coşkun and Jürgen Zeidler, "'Cover Names' and Nomenclature in Late Roman Gaul: The Evidence of the Bordelaise Poet Ausonius" (2003), p. 33.</ref>。
プロト・ケルト語のテオニムの形態は、*''Carno-on-os''として再構築されている。マポノス、エポナ、マトロエナ、シローナなどのように、増大詞の-on-はテオニムの特徴である。はテオニムの特徴である<ref>Delamarre, citing M. Lejeune, ''Lepontica'' (Paris 1971), p. 325.</ref>。マイヤー(Maier(2010))は、Cernunnosの語源は不明だが、ケルト語の「角」または「鹿の角」(Carnonosと同様)に根ざしていると思われると述べている<ref name="Maier">Bernard Maier, [https://books.google.com/books?id=7AvdTqwucfwC&pg=PA69&dq=%22the+etymology+of+whose+name+is+unclear%22&hl=en&ei=2E3ETPjlFcWOnwfrmpHZCQ&sa=X&oi=book_result&ct=result&resnum=1&ved=0CC0Q6AEwAA#v=onepage&q=%22the%20etymology%20of%20whose%20name%20is%20unclear%22&f=false ''Dictionary of Celtic Religion and Culture''] (Alfred Kröner, 1994; Boydell, 2000), p. 69.</ref>。
The [[Proto-Celtic]] form of the theonym is reconstructed as *''Carno-on-os''. The [[augmentative]] ''-on-'' is characteristic of theonyms, as in [[Maponos]], [[Epona]], [[Matronae]], and [[Sirona]].<ref>Delamarre, citing M. Lejeune, ''Lepontica'' (Paris 1971), p. 325.</ref> Maier (2010) states that the etymology of ''Cernunnos'' is unclear, but seems to be rooted in the Celtic word for "horn" or "antler" (as in ''Carnonos'').<ref name="Maier">Bernard Maier, [https://books.google.com/books?id=7AvdTqwucfwC&pg=PA69&dq=%22the+etymology+of+whose+name+is+unclear%22&hl=en&ei=2E3ETPjlFcWOnwfrmpHZCQ&sa=X&oi=book_result&ct=result&resnum=1&ved=0CC0Q6AEwAA#v=onepage&q=%22the%20etymology%20of%20whose%20name%20is%20unclear%22&f=false ''Dictionary of Celtic Religion and Culture''] (Alfred Kröner, 1994; Boydell, 2000), p. 69.</ref>
"Cernunnos" is believed by some Celticists to be an obscure epithet of a better attested Gaulish deity; perhaps the god described in the [[interpretatio Romana]] as [[Mercury (mythology)|Mercury]] or [[Dis Pater]],<ref name="Anne Ross 1967"/> which are considered to share Cernunnos's [[psychopomp]] or [[chthonic]] associations. The name has only appeared once with an image, when it was inscribed on the ''[[Pillar of the Boatmen|Nautae Parisiaci]]'' (the sailors of the [[Parisii (Gaul)|Parisii]], who were a tribe of [[Gauls]]).<ref name=Breviary2005>{{cite book|title=Celtic Culture: A Historical Encyclopedia|last1=Breviary|first1=A.|editor1-last=Kock|editor1-first=John T.|publisher=ABC-CLIO|volume=1|edition=|year=2005|chapter=Celticism|pages=396|isbn=978-1851094400|url={{Google books|plainurl=yes|id=f899xH_quaMC|page=396}}}}</ref> Otherwise, variations of the name Cernunnos has also been found in a Celtic inscription written in [[Greek alphabet|Greek characters]] at [[Montagnac, Hérault|Montagnac]], [[Hérault]] (as καρνονου, ''karnonou'', in the [[dative case]]).<ref>Xavier Delamarre, ''Dictionnaire de la langue gauloise'' (Éditions Errance, 2003), pp. 106–107.</ref> A [[Vulgar Latin|Gallo-Latin]] [[adjective]] ''carnuātus'', "horned", is also found.<ref>Equivalent to Latin ''cornutus'', "horned"; Delamarre, citing J. Vendryes, ''Revue Celtique'' 42 (1925) 221–222.</ref>