If you try to find synonyms for the word "original source", you can easily see that there are not so many of them and all of them only partially reveal the meaning of this term. The lexemes closest in meaning are: source, root cause, beginning, origin.
Definition in dictionaries
Canonical definitions of the word "original source" come down to its two meanings. The first is something that gives rise to or is the basis of something. The second meaning, in which this word is most often used, is the original source of information. As a rule, in the second case, it is most often about a document, or about an eyewitness, or about a direct participant in an event. At the same time, it is not at all necessary that this very source of information be truthful. Any lie is also born somewhere and also has its starting point, from where it begins its journey. Thus, the source is a word denoting the place or object of the occurrence or fixation of the occurrence of an event or information.
Transmission links
The primary source of information is an extremely important element of public life, especially in the conditions of instant dissemination of any information. In the process of transmission, for various reasons, information is subjected to certain distortions and conjectures, like a child's game of a damaged telephone, which often leads to a change in meaning to the opposite. In this case, distortions can be made absolutely consciously. And such actions are the basis of propaganda, the purpose of which is to create an appropriate public opinion regarding certain events. Therefore, people who want to have real information about reality must, in any case, look for and find the primary source of the information that has appeared. Even in cases where the information occasion is covered with a veil of artificial sacredness. The original source is the cornerstone of the truth test.