The 1841 tithe map of Eglwysilan parish, shows Rhydyfelin consisting of small farms and a few cottages. One of the farms that appear on the map is Ynis Rhydfelen and this may provide evidence in the argument about the derivation of the place name Rhydyfelin. The name Rhydyfelin indicates that a mill on the ford was once there. However, others argue that the village should be named Rhydfelen, ‘the yellow ford', probably a reference to the colour of the clay. It was an erroneous belief by some that this was a corruption of Rhydyfelin, which influenced the Ordnance Survey to record it as such in 1885. It's likely that this form arose from a misconception, since there is no record of a mill at this place.
Rhydyfelin, the Glamorganshire Canal and the Doctor's Canal in their early development, were a result of two aqueducts. They flowed side by side, more or less, through the village towards the southeast before joining in Dynea. The Glamorganshire Canal stretched from Merthyr Tydfil to Cardiff whilst the Doctor's Canal, a mile long, connected the end of the tram tracks with the main canal. As the name suggests, it was a trained doctor named Richard Griffiths who opened the Doctor's Canal in 1813. Griffiths would often shirk his medical duties as he found the development in the coal industry to be more interesting.