One of the unique challenges of a constructed language, in my mind, is how they handle the way in which language longs to break rules. In other words, how does constructed language handle slang?

For the most part, the entire notion of underground language runs entirely contrary to the notion of constructed language, where the rules are strictly prescribed.

However, in unique cases where conlangs have had time to brew with native speakers, such as with Esperanto, have we seen specific examples of slang develop within the language? What conditions seem to prompt the development of slang terms in such circumstances?

  • I wonder whether your question is general (as most of the wording including the title suggest) or concerning Esperanto (as the last paragraph and the tag suggests). I think, the answers would be quite different in both cases (although both may point to Esperanto; the former as an example.)
    – Jan
    Commented Feb 10, 2018 at 10:22
  • 1
    I would like to make the comment that “where the rules are strictly prescribed” is not necessarily true. This is certainly the situation in auxlangs and loglangs, but many creators of the more experimental or artistic conlangs don’t care or even encourage speakers (if there are any) to innovate idioms, slang etc, because those are part of any natural language, and so in striving to imitate natural languages you obviously have to come up with ways speakers break the rules. And what easier way to do so than just have the speakers decide themselves how they want to do it? Commented Feb 10, 2018 at 12:34
  • @Adarain thanks for making that comment, I think that's an important point. Commented Feb 10, 2018 at 14:00
  • Related question on the Esperanto SE: esperanto.stackexchange.com/questions/389/…
    – Sir Cornflakes
    Commented Feb 10, 2018 at 18:55

2 Answers 2


Wiktionary has a list of Esperanto internet slang but most of these I've never seen or heard used before (at least in the main esperanto chats on Telegram).

Esperanto slang terms I've heard or used

  • krokodili - to speak in a language other than esperanto in a group of esperantists. No one really knows where it originated but the most popular story seems to be that it's because crocodiles have big mouths and small brains. "Ne krokodilu" is a very commonly used phrase.
  • sal - hi (short for saluton)
  • kvf - how are you (abbreviation of kiel vi fartas)
  • mdr - lol (multe da ridoj)
  • mns - idk (mi ne scias)


  • ho ve (occasionally just "ve") - oh geez
    (according to this post on Esperanto SE the literal translation is "oh woe" but who says that)
  • 8, ok, okej - k, ok, okay
    ("ok" is the word for eight in Esperanto, mdr.)
  • ho - oh
  • jes ja - yes, indeed
    (according to this post on Esperanto SE "ja" can be used in other situations, but I have never heard or seen it used other than after "jes")
  • Fek' - f*ck
  • Kio la fek - what the f*ck
    (This is an obvious anglicism and considered "grammatically incorrect" by many esperantists, who will tell you it's actually kio feke)
  • Volap*ko - "the v word". More offensive than all the offensive words you know combined.
  • (Just to be clear, the last point was nothing but a bit of banter. Volapük tried its best.)
    – as4s4hetic
    Commented Feb 10, 2018 at 10:21
  • krokodili is like Anc. Greek usage of thinking all foreigners say 'bar-bar', which were called bar-barians.
    – Duncan
    Commented Feb 21, 2018 at 19:41

In Esperanto, the word knuflo is mainly used by young people, who participate in local meetings, around the dutch-speaking regions of Flanders and the Netherlands. It is almost not used in international context, like on the Internet ("knuflo" esperanto gives less than 12 results with Google), outside of groups that are community specific. Outside of these groups, the word is not understood.

Knuflo is like hugging, but longer, with more parts of the body. It is like cuddling, but it is hard to describe. Users say you have to receive a knuflo to understand it, and you have to experience it to understand why the word is needed in the language.

So here, you have three factors. People sharing the same factor tend to speak together. When people speak mainly within their own community, slang appear.

  • Age factor: Young people coin new words for the new environment, and for concepts that are felt important for the social group. It is exactly the same in Esperanto. But there is no clear barrier. Here is a footage of an older person using the word "knuflo".

  • Location factor: Not all Esperanto-speakers participate regularly in Esperanto events, in fact only a minority do. There is an event-slang, with words such as "gufujo", "stelo (mono)", etc. Esperanto events are often attended by people from neighboring countries. This way local slang is shared among people of different countries and age. Because of this, you can sometimes hear "knuflo" in French-speaking Belgium and Germany (near the Netherlands). The word is also shared in huge international youth events like JES and IJK, where a consequent number of participants come from the knuflo-region.

  • Language factor: "knuflo" comes directly from the Dutch verb "knuffelen". Dutch-speaking beginners who are not aware of similar words like "brakumo" "kareso" "dorlotado" are more likely to remember and understand "knuflo". This kind of beginner-slang tend to not go outside the local club, but "knuflo" is an odd exception. Maybe because some local experienced speakers think it brings new meaning.

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