S. Argonui m.
The 8th chieftain of the Dúnedain (LotR/1038). The initial element of his name is the prefix ar(a)- “noble”. The remainder of the name might be the noun caun (in any of its various meaning) with the adjectival suffix -ui (as suggested by David Salo, GS/246, 342).
References ✧ LotRI; PMI
Elements
ar(a)- | “noble, royal, high” |
caun¹ | “prince, chief, head” |
-ui | “-ful, having quality, adjective suffix; [as verbal suffix] possibility, suitability, *-able” |