why to use keyword "carrier"?

[anlexN]

why not use keyword "header"?

what tech consideration is it? where is this concept from?

[farzinlize]

the term carrier is used because it carries the context for propagation and the HTTP header is just only one of the solutions that can carry contexts between different processes or services. You may consider using other forms of carriers such as a custom TextMapCarrier with unordered_map in c++, to propagate contexts between threads of the same process or between services that are connected through sockets or something else rather than HTTP