 Alternative hypotheses (not nearly as accepted) are that "marteloio" is a corruption of "mari logio" (meaning "rule of the sea"), or from "mare tela" (meaning "sea network"), or that it derives from the Greek "homartologium" ("όμαρτόλογίον", meaning "companion piece"), or from the Greek "imeralogium" ("ήμερόλογίον", meaning "daily calculation") or that it might be from the northern French "matelot", which in turn comes from Breton "martolod" (meaning "sailors").The "rule of marteloio" was used in European navigation in the Middle Ages, most notably in the Mediterranean Sea between the 14th and 16th centuries, although it may have older roots.It was an integral part of navigation by "compass and chart", before the advent of geographical coordinates and the development of celestial navigation in Europe.