sarn (“stone as a material”) cebir (pl. of ceber “stake, spike”)
Sarn Gebirnoun. stone spikes
sarn gebirplace name. rapids of the spikes, Stone-spikes
A series of rapids on the river Anduin described as “sharp shelves and stony teeth” (LotR/391) and translated “Stone-spikes” (RC/327). This name is a combination of sarn “stone” and the plural of the lenited plural of ceber “spike” (SA/sarn, RC/327). This formation is somewhat odd, since nouns in this position are not usually lenited in Sindarin, though they were in earlier Noldorin. The form Gebir may be a hold-over of its early Noldorin name.
Conceptual Development: In Lord of the Rings drafts from the 1940s, these rapids were first named N. Pensarn, quickly revised to N. Ruinel >> Sarn Ruin (TI/366), and a bit later to (plural) Sern Gebir >> Sarn Gebir (TI/283). These last two forms also appeared in the Etymologies with an unclear gloss, perhaps “?lonestone” or “?limestone”, but they were struck out (Ety/KEPER, EtyAC/KEPER).