Why does SQL Server use "Binn" directory instead of "Bin"
Haidong Ji, who authored a few books on SQL Server, claims that this is a historic leftover from the 16-to-32-bit migration:
By the way, do you know why the folder is called Binn? Why two “n”s? There is a bit of history there. Back in the 16-bit days, all binary files were stored under the Bin folder. However, as things moved to 32-bit and Windows NT came to the market, this new folder, Binn, was created to accommodate that. The extra n was taken from NT, which stands for “New Technology”.