 For the majority of its history the area now recognised as the Rhondda Valley was an exclusively Welsh speaking area . It was only in the early 20th century that English began to supplant Welsh as the first language of social intercourse . In 1803 , English historian Benjamin Heath Malkin mentioned while travelling through Ystradyfodwg , that he had only met one person with whom he could talk , and then with the help of an interpreter . This situation was repeated with John George Wood , who on his visit to the area complained of the awkwardness of understanding the particular dialects and idioms used by the native speakers , which were on times difficult for other Welsh speakers to understand . This dialect was once called ' tafodiaith gwŷr y Gloran ' ( ' the dialect of the men of Gloran ' ) . 
