sîr (“river”) + annon (“great door or gate”)
noun. gate river
sîr (“river”) + annon (“great door, gate”)
proper name. Gate-stream
Conceptual Development: In Lord of the Rings drafts from the 1940s, this name was already as N. Sirannon (RS/445).
Word Gloss sîr “river, stream” annon “(great) gate, door”