This chapter describes the German originator of the idea of accident proneness, Karl Marbe. Marbe had already shown an interest in errors in speech and writing in connection with his interest in linguistics. He was acquainted with psychological research that suggested variations on the statistical normal curve. Marbe was using a chemical metaphor, Unfallaffinität or accident affinity. His definitive publication on accident proneness (Unfallneigung) was his book of 1926 summarizing his thinking. Additionally, he had succeeded in bringing into applied psychology and safety literature some familiarity with the concept of accident prone people. Many people concerned with accidents simply ignored Marbe's ideas. British experts developed the idea of accident proneness in ways that found better institutional support, or at least receptivity, than did Marbe's initiative.