source language

noun
  1. the language in which a text appears that is to be translated into another language.Compare target language(def 1).
  2. a language, usually the learner's native language, that is a source of interference in learning another language.Compare target language(def 2).

Origin of source language

First recorded in 1955–60
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018