A noun appearing as N. cirban “haven” in The Etymologies of the 1930s as a combination of N. ceir “ship” [vs. S. cair] and N. pann “courtyard” (Ety/PAN), so more literally “*ship-enclosure”.

Neo-Sindarin: Some Neo-Sindarin writers instead use ᴺS. círbann as suggested in Hiswelókë’s Sindarin Dictionary (HSD), with the long í inspired by S. círdan (as opposed to N. cirdan), and long final -nn in disyllables being a common convention in Neo-Sindarin of the 2000s, as suggested by Helge Fauskanger. Personally I would just stick with attested cirban.