sîr (“river”) + annon (“great door, gate”)
Sindarin
Sirannon
noun. gate-stream
Sirannon
noun. gate river
sirannon
proper name. Gate-stream
The stream flowing past the doors of Moria translated “Gate-stream” (LotR/300), a combination of sîr “river” and annon “gate” (SA/sîr, annon).
Conceptual Development: In Lord of the Rings drafts from the 1940s, this name was already as N. Sirannon (RS/445).
Elements
Word Gloss sîr “river, stream” annon “(great) gate, door”
sîr (“river”) + annon (“great door or gate”)