The river was called many different names; at times different parts of the river were known by different names. The present name of the river dates to 1805–1808, when Spanish explorer Gabriel Moraga was surveying east from Mission San José in order to find possible sites for a mission. Moraga named a tributary of the river (it is not known which one) for Saint Joachim, husband of Saint Anne and father of Mary, the mother of Jesus. The name Moraga chose was later applied to the entire river; it was in common use by 1810.