krokodilo

This animal gave the Esperanto movement its best word. Krokodili is to speak a language other than Esperanto at an Esperanto event, and normally your own: the verb is krokodilo with -i on it, doing exactly what the four endings always do. Being told ne krokodilu! at a congress breakfast is a friendly telling-off, almost always delivered by somebody who was doing it an hour earlier. There is no other constructed language whose central social sin is named after a reptile, and there is no other word that so completely gives away that Esperanto has a community rather than a user base.

Nobody knows why the crocodile. Three stories circulate: that crocodiles have big mouths and flap them, that a Paris Esperantist named Ferrari asked what those crocodiles at the back wanted, and that Andreo Cseh's teaching method passed a wooden crocodile to whoever lapsed into their own language. All three are told with total confidence and none of them is documented. The verb itself is solid, with a dictionary entry and a citation, unlike the reptiles that grew up around it - aligatori, kajmani, gaviali - which are community inventions with a Vikipedio page and no dictionary at all. The whole family, with an honest note on which are attested, is set out in the spoken register.

The animal is still the animal. In an ordinary sentence krokodilo means a crocodile in a river, with the teeth and the patience, and Esperanto keeps the alligator separate as aligatoro. What is worth noticing is the direction of travel: the slang came from the beast, not the other way round, and a learner who meets krokodili first and assumes the animal is named after the habit has the whole thing backwards.