The aim of this paper is to illustrate the distinction of Irish English from the Standard English, especially in lexicon. The first part covers the history, geography and demography of the development of Ireland itself stating the historical facts that have had an impact on the language development. Later on in the paper, phonological, morphological and syntactical differences in usage are stated. The comparison and the varieties of Irish English dialects are depicted. Every part of the paper is supported with examples. The most important part of the paper is on lexicographical peculiarities that are specific to Irish English. How the lexical development started, the borrowings from Irish, the Celtic impact, new words and derivatives are topics dealt with in that chapter.