The name is Indian, and signifies " The Place where the Fresh water falls into the Salt," and describes the unusual natural fact, that the bed of the Mamaroneck River some distance above the place of the present bridge connecting it with the town of Rye, (at which place a bridge did not exist till the year 1800) was originally crossed by a ledge of rocks sufficiently high to prevent the tide rising above it, over which the fresh water fell directly into the salt water, and at low tide with a strong rush and sound. The Indians gave the name to the place of this uncommon occurrence and to the River itself

In the earliest deeds and documents, the word is spelled " Momoronock," " Mamoronack " and " Mamaranock ; " the modern spelling does not seem to have obtained generally till toward the middle of the eighteenth century. Very many ways of spelling this word are met with, but all evidently aiming at expressing its Indian sound. The Indians having no written language, all their names and other words which we now have, are based upon the reproducing of their spoken sounds in our letters. If a Dutchman, Frenchman or an Englishman, undertook to write the same word from an Indian's mouth, very different looking and sounding words would be produced. And as very many of our New York Indian terms and names represent an English spelling of a Dutch or French translation of an Indian sound, we should never be surprised at any variety of spelling.'