Given name of the 8th king of Gondor (LotR/1038). This name seems to be a compound of tar- “high, king” and the plural form of -sta “land”.
Quenya
Tarostar
lord of ostar [?]
tarostar
masculine name. ?King of the Lands
Elements
Word Gloss tar- “high, high; [ᴹQ.] king or queen (in compounds)” -sta “land, part, part; [ᴹQ.] close grouping, land”
Tarostar masc. name, *"Lord of ostar [?]" (Appendix A)