Complex sentence: The first femslash story probably emerged in the mid-to-late 1970s; the material probably did not have a name then, for the term slash did not appear until at least 10 years later.
Split into simpler sentences: The first femslash story probably emerged in the mid-to-late 1970s. The material probably did not have a name then, because the term "slash" did not appear until at least 10 years later.