The article describes ethnic idioms and their functioning in English. The research is aimed at differentiating national stereotypes in the English linguistic mentality basing on ethnic idioms and compiling an onomasiological portrait of representatives of different ethnic groups based on a comprehensive analysis of modern ethnic idioms used in English. The author studies ethnic idioms selected from the phraseological dictionaries and sites. The research is based on the conceptual analysis, definitional analysis, contextual analysis, etymological analysis, semantic analysis, and sociolinguistic analysis. In the course of the study, the author revealed the most common stereotypes for the Dutch, differentiated some meanings enabling to create an image of a contemporary Dutchman built up in the linguistic mentality of a typical Englishman. The results of the research may be applied in further studies in the spheres of sociolinguistics, ethnoconflictology, history, and political science.