The aim of this research is to describe the results of the endings -anum, -anam, -anos and -anas in the municipality of Castrelo do Val, in the region of Verín, in the whole of Galician and in the Galician-Portuguese dialect continuum. The data come from the Atlas Lingüístico Galego (ALGa), the Atlas Lingüístico de la Península Ibérica (ALPI), the work of Rodríguez Lorenzo (NEnq 2022), and other research, including our own field research. For the long-term variation of the endings mentioned, toponymic data and examples from past texts were used. The fundamental change consisted in simplifying the complex syllable, especially in the plural verbs (-auns). The resulting changes made the central-eastern variant the main variant of common Galician, which preserves specific forms (with imperceptible nasality, which is not written) for masculine and feminine and for their plurals. The western system eliminates the generic difference of the medieval elements in the singular and plural forms by losing the glide of the diphthong of masculine words or by making it imperceptible. This results in a further departure from the medieval forms with the central-eastern system, although not as much as some Portuguese dialectal varieties. The central-eastern and western systems are the result of the convergence that took place between neighbouring territories with continuity of population over a long period of time, which allowed the elimination of their variation (-aun / -au / -án). Between the two aforementioned systems, there is a hybrid area with a variety of results, in which the central-eastern forms are gradually prevailing. In non-western territory, there are conservative places with ‑án and [ã], and innovative places featuring -ou.