[1] Eugen Feller was a famous chemist and created Elsa fluid named after his mother[clarification needed].

According to Gian-Carlo Rota, Eugen Feller's surname was a "Slavic tongue twister", which William changed at the age of twenty.

He is remembered for his championing of probability theory as a branch of mathematical analysis in Sweden and the United States.

[8] By stimulating his colleagues and students in Sweden and then in the United States, Feller helped establish research groups studying the analytic theory of probability.

Feller made fundamental contributions to renewal theory, Tauberian theorems, random walks, diffusion processes, and the law of the iterated logarithm.