GR translation: some kind of brain nausea here

[Mike Jing]

V206.19-25, P208.37-209.6   “Recall your ancient German runes,”
suggests Sir Stephen Dodson-Truck, who is from the Foreign Office
P.I.D. and speaks 33 languages including English with a strong Oxonian
blither to it.
       “My what?”
       “Oh,” lips compressing, some kind of brain nausea here, “that
coil symbol there happens to be very like the Old Norse rune for ‘S,’
sôl, which means ‘sun.’ The Old High German name for it is sigil.”
       “Funny way to draw that sun,” it seems to Slothrop.

What is "brain nausea" exactly? Is it a reaction to Slothrop's
ignorance, or is it something else?
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Pynchon-l / http://www.waste.org/mail/?list=pynchon-l