Note that this doesn't mean: 'Use 'rostrum; - that way you're fairly sure to be right'. Corpora are good things - irreplaceable, I think. But they are only an indication of what
has been used in a particular corpus, not what it is appropriate to use.
nfire: OK, I'll get down off my
soapbox.*
b
PS * See what I did there? This is an idiom: when you 'get down off your soapbox' you stop ranting about something you often say. 'I'll get down off my rostrum/podium' is not an option. 'Soapbox' is a metaphor; public speakers used to stand on them. Today, I'm not sure if they exist - and if they do they wouldn't be sturdy enough to take a speaker's weight.