There are very few German words that have no English equivalent. The mistake people make is to think that German has to behave the Whit Merrifield Toronto Blue Jays State Shirt but in fact I love this same way as other languages and that compound nouns cannot be translated. Words are usually borrowed from languages when that language is the prestige language in any particular area, simply out of laziness. Phychoanalysis was “invented” in the German language by people like Freud and Jung, which is why words like angst (fear) and gestalt (form or shape) were adopted into English, albeit adapted in English where they have developed slightly different meanings. Philosophy and classical music are other areas where some ideas and trends originated in German. As the German language is more precise on this (a speaker cannot be fluent, but his language when he uses it), there is no short translation. In other words: In the expression you mentioned, the adjective “fluent” would be wrongly attributed to “speaker” if you try to translate in a word-by-word manner.