Invented in the late 1870s, Volapük was the first international auxiliary language to achieve widespread success (it claimed approximately a million speakers at one point).
Its grammar was broadly German (including inflection for noun cases) while its vocabulary was mostly English, but highly distorted, to the point of unrecognisability. (The name of the language itself consists of vola “world” + pük “speak” – both those words are considered borrowed from English!)
Volapük was eclipsed within a couple of decades by Esperanto, which was much more regular and easier for people to learn. While I’ve mostly referred to the language in the past tense here, there are an estimated ~20 people still speaking the language today.
The word “volapuk” has been borrowed into a few languages with different meanings. In Esperanto, volapukaĵo means “something unintelligible”. Apparently volapyk is also a word in Danish, likewise meaning “gibberish”. And apparently in Russian the term “Volapük encoding” (translated into Russian, obvs) refers to the practice of “transliterating” Cyrillic into the Latin alphabet by picking letters that look similar instead of letters with the same sound.