This distribution appears to have been first derived by Schrödinger in 1915 as the time to first passage of a Brownian motion.[4] The name inverse Gaussian was proposed by Tweedie in 1945.[5] Wald re-derived this distribution in 1947 as the limiting form of a sample in a sequential probability ratio test. Tweedie investigated this distribution in 1957 and established some of its statistical properties.