Younger son of the 28th king of Gondor Telumehtar (LotR/1038), his name seems to be a combination of ar(a)- “noble” and cirya “ship”.
Quenya
Arciryas
royal ship
arciryas
masculine name. *Noble Ship
Elements
Word Gloss ar(a)- “noble, high” cirya “(sharp-prowed) ship; swift gliding, (sharp-prowed) ship, [ᴹQ.] boat; [Q.] swift gliding”
Arciryas masc. name (evidently derived from *arcirya "royal ship") (Appendix A)