"I am still curious about "emic" terminology and (in America) its history and internal variation."

If you want to know the local contemporary terminology, check the local ordinances of the period fory your town or city (or the nearest one, if your location is rural).  
I have been hoping that someone would step in and reply, because I can't remember the details ...
I think it was Pat Garrow & Co's study of the DC center, in which they reviewed local ordinances.  They showed that there were different ones to control different types of waste disposal.  Using a similar process in Braddock, PA, for the late 19th/early 20th century, I found the first rules were to regulate the wagons that removed nightsoil from privies. There were later ones about "rubish" and finally ones for coal ash (waste from burning coal for heating/cooking).  Since that was the least offensive type of waste, it seems to have been regulated last. Finally, there were ones requiring hook up to sewers (restaurants and slaughter houses first, everybody else later).  
I can't lay my hands on the details, and the terminology may vary, which is why I suggest you check your local ones.  I just went into the municipal office and asked to look over their early ordinances.  The ones I wanted were mixed in with ones about street paving, telephone poles, pigs in the street, and all sorts of curious and entertaining matters. I had never realized that realing local laws could be fun or funny.
 
Personally, I use "historic deposit" for most artifact-bearing soil accumulations, having dealt mostly in yard deposits mixed with or overlying the A horizon.  I use "midden" for the especially high density deposits, or for areas rich in faunal remains.  I have only used "dump" for "field dumps" - concentrations in a small area, far from the residence, usually from a short time period.  But that is all in technical reports.  When talking to or writing for the public, I would not hesitate to use terms like trash dump, trash scatter, garbage, or anything that will get the point across and not sound like unnecessary jargon where a plain word will do.
Meli Diamanti