Angst is fear or anxiety (anguish is its Latinate equivalent, and the words anxious and anxiety are of similar origin). The dictionary definition for angst is a feeling of anxiety, apprehension, or insecurity.
The word angst was introduced into English from the Danish, Norwegian, and Dutch word angst and the German word Angst. It is attested since the 19th century in English translations of the works of Søren Kierkegaard and Sigmund Freud. It is used in English to describe an intense feeling of apprehension, anxiety, or inner turmoil.
In other languages (with words from the Latin pavor for "fear" or "panic"), the derived words differ in meaning; for example, as in the French anxiété and peur. The word angst has existed in German since the 8th century, from the Proto-Indo-European root , "restraint" from which Old High German angust developed. It is pre-cognate with the Latin angustia, "tensity, tightness" and angor, "choking, clogging"; compare to the Ancient Greek ἄγχω (ánkhō) "strangle". It entered English in the 19th century as a technical term used in Psychiatry, though earlier cognates existed, such as ange.
Philosophy of Søren Kierkegaard#Dread or anxiety
In existentialist philosophy, the term angst carries a specific conceptual meaning. The use of the term was first attributed to Danish philosopher Søren Kierkegaard (1813–1855). In The Concept of Anxiety (also known as The Concept of Dread), Kierkegaard used the word Angest (in common Danish, angst, meaning "dread" or "anxiety") to describe a profound and deep-seated condition. Where non-human animals are guided solely by instinct, said Kierkegaard, human beings enjoy a freedom of choice that we find both appealing and terrifying. It is the anxiety of understanding of being free when considering undefined possibilities of one's life and the immense responsibility of having the power of choice over them. Kierkegaard's concept of angst reappeared in the works of existentialist philosophers who followed, such as Friedrich Nietzsche, Jean-Paul Sartre, and Martin Heidegger, each of whom developed the idea further in individual ways.