Please do not create a "key" anywhere on the forum for the names of clients. I would think that such would definitely be a violation of the ICA, and would undermine the shared value on this forum of not giving away the research each one of us does in finding the clients that we want to shop.
Beyond that, we already would never mention a client's name and then use an abbreviation or acronym for the MSC in the same thread. Such would be a clear violation of the ICA.
If, however, the OP wants a listing of the common terms, abbreviations and acronyms (but nothing that identifies a client!) used around here, I'm sure that would be easy to accomplish, e.g. (exempli gratia - for example)...
ICA - Independent Contractor Agreement
OP - Original Post(er) (the first entry or author on a thread)
MSC - Mystery Shopping Company
GS - Gas Station
FF - Fast Food
CoRI, Cori, CORI, cori, and sometimes CRI - Corporate Research International
GFK, GfK - GfK Mystery Shopping (the acronym is part of their name)
MF - Market Force (or an obscenity that conveys the sentiments of some shoppers concerning MF)
"chicken littles" - a pejorative expression unique to this forum sometimes used to describe shoppers who run around snatching up all the shops that they can as if the sky is falling, rather than waiting for the shops to go up in price
... etc. (et cetera - and other things)