The Hampdenshire Wonder by J.D. Beresford

Then that almost voiceless child found words. Heathcote's announcement of lunch was waved aside, the long afternoon waned, and still that thin trickle of sound flowed on.

The Wonder spoke in odd, pedantic phrases; he used the technicalities of every science; he constructed his sentences in unusual ways, and often he paused for a word and gave up the search, admitting that his meaning could not be expressed through the medium of any language known to him.