Maisy is a Scottish pet form of Margaret, by way of the Gaelic Mairead, and so goes back to the Greek margarites and means "pearl". Lucy Cousins's picture-book mouse Maisy has made the name familiar to a whole generation of toddlers. The spelling with a y is rarer than Maisie in the United States; Maisy entered the top 1000 in 2022 and has climbed to number 745 in 2025, its best rank so far.