the greco-egyptian scientist ptolemy referred to the larger island as "great britain" (μεγάλη βρεττανία "megale brettania") and to ireland as "little britain" (μικρὰ βρεττανία "mikra brettania") in his work "almagest" (147–148 ad). in his later work, "geography" (c. 150 ad), he gave the islands the names "alwion", "iwernia", and "mona" (the isle of man), suggesting these may have been the names of the individual islands not known to him at the time of writing "almagest". the name "albion" appears to have fallen out of use sometime after the roman conquest of britain, after which "britain" became the more commonplace name for the island.