ᴹ√GIR root. “quiver, shudder”
A (Noldorin-only?) root in The Etymologies of the 1930s glossed “quiver, shudder”, with derivatives N. gir- “to shudder” and N. girith “shuddering” (Ety/GIR). The continued appearance of Sindarin names containing this last word such as S. Girithron “December, *Shuddering-one” (LotR/1110) and S. Nen Girith “Shuddering Water” (S/220) strongly indicates the continued validity of this root.
Reference ✧ Ety/GIR ✧ “quiver, shudder”