Where can I get a file/list of the common and scientific names of species?
Maybe not a direct answer to your question, depending on what you mean with "unencoded data file", but the Global Biodiversity Information Facility (GBIF) has an API where you extract data for species names. Their database includes common names (aka vernacular names) when they have that, and often common names from different languages. Using this API, you can extract data and construct a name file for a particular taxa that you are interested in.

As an example, this is the list of the first 20 vernacular names found for Passer domesticus (House sparrow):

{
   "endOfRecords" : false,
   "results" : [
      {
         "language" : "",
         "sourceTaxonKey" : 100220560,
         "source" : "Global Invasive Species Database",
         "vernacularName" : "English sparrow"
      },
      {
         "language" : "",
         "sourceTaxonKey" : 100220560,
         "vernacularName" : "Europese huismuis",
         "source" : "Global Invasive Species Database"
      },
      {
         "vernacularName" : "Gorrion domestico",
         "source" : "Global Invasive Species Database",
         "language" : "",
         "sourceTaxonKey" : 100220560
      },
      {
         "source" : "Integrated Taxonomic Information System (ITIS)",
         "vernacularName" : "GorriÃ³n casero",
         "language" : "spa",
         "sourceTaxonKey" : 102101640
      },
      {
         "vernacularName" : "Gorrión Común",
         "sourceTaxonKey" : 123213203,
         "language" : "spa"
      },
      {
         "language" : "spa",
         "sourceTaxonKey" : 101186844,
         "source" : "The European Nature Information System (EUNIS)",
         "vernacularName" : "Gorrión Común"
      },
      {
         "language" : "spa",
         "sourceTaxonKey" : 114130266,
         "source" : "Colaboraciones Americanas Sobre Aves",
         "vernacularName" : "Gorrión casero"
      },
      {
         "vernacularName" : "Gorrión casero",
         "source" : "Yanayacu Natural History Research Group",
         "sourceTaxonKey" : 119245200,
         "language" : "spa"
      },
      {
         "vernacularName" : "Gorrión casero",
         "source" : "Catalogue of Life",
         "sourceTaxonKey" : 119950016,
         "language" : "spa"
      },
      {
         "language" : "swe",
         "sourceTaxonKey" : 101186844,
         "vernacularName" : "Gråsparv",
         "source" : "The European Nature Information System (EUNIS)"
      },
      {
         "vernacularName" : "Gråspurv",
         "language" : "dan",
         "sourceTaxonKey" : 123213203
      },
      {
         "vernacularName" : "Gråspurv",
         "language" : "nob",
         "sourceTaxonKey" : 123213203
      },
      {
         "language" : "deu",
         "sourceTaxonKey" : 116795880,
         "vernacularName" : "Haussperling",
         "source" : "Taxon list of animals with German names (worldwide) compiled at the SMNS",
         "country" : "DE"
      },
      {
         "language" : "deu",
         "sourceTaxonKey" : 100483595,
         "source" : "Belgian Species List",
         "country" : "BE",
         "vernacularName" : "Haussperling"
      },
      {
         "language" : "deu",
         "sourceTaxonKey" : 123213203,
         "vernacularName" : "Haussperling"
      },
      {
         "sourceTaxonKey" : 101186844,
         "language" : "deu",
         "source" : "The European Nature Information System (EUNIS)",
         "vernacularName" : "Haussperling"
      },
      {
         "source" : "The Clements Checklist",
         "vernacularName" : "House Sparrow",
         "language" : "eng",
         "sourceTaxonKey" : 113987294
      },
      {
         "vernacularName" : "House Sparrow",
         "source" : "Taxonomy in Flux Checklist",
         "language" : "eng",
         "sourceTaxonKey" : 100159046
      },
      {
         "source" : "Colaboraciones Americanas Sobre Aves",
         "vernacularName" : "House Sparrow",
         "language" : "eng",
         "sourceTaxonKey" : 114130266
      },
      {
         "sourceTaxonKey" : 102101640,
         "language" : "eng",
         "vernacularName" : "House Sparrow",
         "source" : "Integrated Taxonomic Information System (ITIS)"
      }
   ],
   "limit" : 20,
   "offset" : 0
}


Using this type of search: api.gbif.org/v1/species?name=Passer%20domesticus, you can look for all info for a particular species, starting from either a scientific name or a common name (in example, Passer domesticus). 

GBIF includes information in 1,643,948 species (and counting), but I don't know for what proportion they have common names (or where there are common names).