 This ultimately led to the notion of a compact operator as an offshoot of the general notion of a compact space.It was Maurice Fréchet who, in 1906, had distilled the essence of the Bolzano–Weierstrass property and coined the term "compactness" to refer to this general phenomenon (he used the term already in his 1904 paper which led to the famous 1906 thesis).However, a different notion of compactness altogether had also slowly emerged at the end of the 19th century from the study of the continuum, which was seen as fundamental for the rigorous formulation of analysis.