1. Irish Anglicised form of Riona from Gaelic "queen".
2. English short form or pet name for girl's names ending in "-rina", see examples, above. [See also Ina.]
It has long been a practice in Scotland for girls' names to be formed from a boy's name with the addition of -ina at the end [e.g. Peterina, Hectorina, Arthurina, etc]. Occasionally the boy's name has been slightly modified to make for a more melodious name, e.g. Alexandrina from Alexand(e)r + -ina
Note that the -ina/-rina ending also occurs on relevant names in some old documents in Latin - with appropriate case modifications.
For a full list of names on this site ending in -rina, search on *rina.