A ford across the river Gelion translated “Ford of Stones” (S/92), its name is a combination of sarn “stone” and athrad “ford” (SA/sarn, thar).
Conceptual Development: The name dates back to the earliest Lost Tales and developed as follows: G. Sarnathrod “Stony Ford” (LT2/236) >> N. Sarn-athra/Athrasarn (SM/133, 244) >> N. Sarn Athrad “Stone of Crossing” (LR/406) >> S. Sarn Athrad “Ford of Stones” (S/92).
sarn (“stone as a material”), athrad (ger. of athra- “river-crossing, ford, way”); #The second element could be interpreted as: ath (prefix “on both sides, across”) + râd (“path, track”)