Can you say the idioms "Sit on" or "Sit Upon" as the verbs to suppress or to choke?

Answer 1

Yes, the phrase "sit on" is very common in journalism and legislation as a synonym for suppress. Reporters and congresspeople often "sit on" an article or a bill, either to stop the release of information (in the journalism case), to "play politics" or to kill a bill (for legislators).

While "sit upon" is roughly equivalent in the English language, it would see far less use.

Answer 2

it depends upon the context of the statement...

"(S)he's going to *sit on* the report because (s)he's fearful of it getting out..." would be fine to say...

the second form seems to be okay as well, but the first one's probably more likely

Answer 3

Perhaps in the ghetto.