Sa pháipéar seo, baintear leas as modheolaíochtaí corpasbhunaithe chun anailís dhiacronach a dhéanamh ar dhá théarma Gaeilge a thagraíonn do shaincheantair thíreolaíocha in Éirinn, is é sin ‘Gaeltacht’ agus ‘Galltacht’, ag tús an 20ú haois agus arís ag tús an 21ú haois. Chuige sin, cruthaíodh dhá shainchorpas tréimhseachán agus baineadh leas as modheolaíochtaí corpais chun anailís a dhéanamh ar úsáid an dá théarma. Cíortar na bríonna éagsúla a bhaineann leis an dá théarma agus rianaítear na hathruithe suntasacha a tharla ar bhrí na dtéarmaí le linn an 20ú haois. Déantar grinnanailís ar chomhthéacs úsáide na dtéarmaí trí thorthaí na gcuardach corpais a iniúchadh. Cuireann an taighde seo leis an taighde atá curtha i gcrích go nuige seo ar fhorbairt agus ar chonstruáil an dá choincheap, ‘Gaeltacht’ agus ‘Galltacht’, trí mhodheolaíochtaí úra corpais a úsáid. Eochairfhocail: an teangeolaíocht chorpais, an tsochtheangeolaíocht, Gaeilge, an Ghaeltacht, an téarmaméadracht In this paper, we use corpus-based methods to undertake diachronic analysis of two Irish-language terms, ‘Gaeltacht’ and ‘Galltacht’, which refer to specific linguistic regions in Ireland, at the beginning of the 20th century and again at the beginning of the 21st century. Two specific-purpose corpora of periodicals from these periods were created for the purposes of this research. The various meanings associated with both terms are examined and the major changes in meaning during the intervening period are mapped and discussed. An in-depth analysis of the corpus search results and contextual usages is carried out. This research builds on prior research undertaken in other fields on the development and construction of these two concepts, ‘Gaeltacht’ and ‘Galltacht’ through the application of new corpus-based methodologies.