§ Sarn-Ruin, Sarn Ruin (TI:318,320)
§ Pensarn (TI:353,360)
These are earlier names of the Anduin’s rapids, called Sarn Gebir in The Fellowship of the Ring.
All names include sarn ’stone as a material; or as adj.’ (SAR-). For ruin (here possibly *’rushing, roaring’) see Rhosfein above (2.39).
Pensarn is perhaps derived from PEN-, PÉNED-, whence N. pend, penn ’declivity’, Q. penda ’sloping down, inclined’; also penn ’slope’ (RC:525) + sarn; thus *’stony slope’.