I found a bunch of good ones in A Collection of Word Oddities and Trivia. Pneumonoultramicroscopicsilicovolcanokoniosis (a miner’s lung disease) is well-known, but hard to work into conversation. I might have more luck with “internationalism.”

I suppose I could teach him the longest word in German, DONAUDAMPFSCHIFFAHRTSELEKTRIZITAETENHAUPTBETRIEBSWERKBAUUNTERBEAMTENGESELLSCHAFT (“the club for subordinate officials of the head office management of the Danube steamboat electrical services”), but my German’s pretty rusty. We’ll try “schreibmaschine”.

So I guess my ultimate goal is to have David discussing typewriter imports. Short words it is, then. Might make for a better conversation.