The term “Killifish” is used for all the fish belonging to the family of Cyprinodontidae and is used worldwide by both enthusiasts and specialists. There is so particular explanation for the preference of this definition as opposed to others, but it would seem that it has been passed down over the years and has became a term which doesn’t only indicate a family of fish but also encompasses the enthusiasm of those who breed killifish.

The Webster’s New World Dictionary (Guralnik ed. 1972) defines the word as an “Americanism”, that’s a word whose meaning has been modified with time and has finally become a peculiarity of the American language. It’s origin is ancient and somewhat mysterious; this must be traced back to 1624 when the Dutch settled in the north east of the United State bringing with them their language. The word “Killi” (derived from the Dutch “Kil” and “Likke”) has changed in the course of time (as do many words with Latin origins) so the translation is brook, stream.

In the state of  New York the tributaries of the Hudson river are still called kills, sign of a well-rooted Dutch tradition. In 1664, the English had the upped hand over the Dutch colonies but isolated settlements in this area still continued to exclusively speak Dutch for the rest of the 17^th century up until the early 1800s.

The Dutch tradition remained strong and it became a custom for the English speaking population to refer to the small, shy fish of the kills as Kill-fish. Fundulus De Kay (1842) states: the common name (Killifish) derives from the fact that it’s present in large quantities in small rivers and estuaries and from the fact that the first Dutch defined it as Kills.

For some time there was confusion due to the fact that all the species of small fish were grouped under the term Killifish even though between themselves and present day Killifish there is no scientific relationship. If we want to find reference to the American use of the word Killifish, one has to trace back to 1788 when a German military surgeon, Johann David Schoepff (1752 – 1800 ) published an article in the “Transactions of the Friends of Natural History at Berlin” when he was in the kills area during the fighting. In this article he described his memories, published in the “Description of North American Fishes” chiefly from the waters of New York which includes a small listing of fish species.

As was to be expected, the syntactic structure was modified and we can find some examples such as “ Killy-fish” (Herbert 1849 ), “Killefish” (Butler 1858), “Kill Fish” or “Killey Fish” (Brown 1876), “Killia-Fish” (Damon 1879) and “Killie-fish” (Samuel 1894) right down to today’s “Killifish” (abbreviation: Killy or Killi singular and Killies in the plural).

All this influenced the scientific classification and it would certainly amaze acquarofiles that in 1792 and German naturalist called J.Walbaum described the Cobitis Killifish, based on Schoepff’s experience. It’s a stranger fact that the word in question was never latinized, as many others were. In 1913, in a catalogue published in New York by Walter Brind the expression “ Toothcarp Group, Egg-laying fishes” appeared; this notwithstanding the fact that the American widely used the word Killifish for North American species belonging to this family (top minnows was another common term). The word Killifish was a favourite, judging by the fact that from 1927 to 1933, many books, catalogues and articles appeared with this term as an undertitle for all the Ciprinodontidi.

Christopher Coates used it as a main title in his “ Tropical fishes as Pets” which was published in 1933. Before World War II, the German acquarofilia, undisputed leader and innovator referred to the Killies as “ Eierlegende Zahnkarpfen “, as also in England the translation “ Egglaying Toothcarps “ was used and was a comprehensive formula for all Cyprinodontidi. After the World War, in all the new literature (American and European), including re-publication, the principal title had become “ The Killifishes “ – being the only, undisputed and preferred description by all the acquarofiles.