Esperanto, the artificial language invented by Dr. L.L. Zamenhof, a Polish philologist, in 1887 — in the hope that it would serve as the universal language — was especially popular among fans in the 1930s and '40s. Its words are based on roots common to many European languages; its spelling is phonetic; its grammar is highly simplified and systematized.

A number of fans have been Esperanto enthusiasts, notably Forry Ackerman and Myrtle R. Douglas, who were among the fans who used Esperanto to coin nicknames (Fojac; Morojo). In addition, some Esperanto expressions crept into Fanspeak, such as "ktp" (from "kaj tiel plu," Esperanto for "and so forth") which is used liberally throughout Fancyclopedia II.

Ed Baker (aka Ejobo in Esperanto) was such a zealous wearer of the Green Star (the Esperanto symbol) that as a member of The Cult he published Fantasy Rotator 116 (1962) entirely in Esperanto. (The Cult immediately found an excuse to drop him and several more to keep him out, but that's another story.)

There was also Dawnish, a language created by Don Wollheim during a period when he was feuding with Ackerman. Dawnish, by definition, was universal, in that no one understood it.

from Fancyclopedia 1 ca. 1944