Yes. Has been since at least the second century BC if you believe the usual chronology.
There is copious information, including the very low incidence of use for girls here on Wikipedia.
Internet searches for images of Rory and Ruairidh reveal how well known the name is. Rory produces one well known female, Rory Gilmore. Although the name Gilmore hints at Scottish ancestry, she was not officially Rory - it is a not-clearly-explained nickname. Ruairidh revealed even fewer females, but one male who is very important if you are learning Gaelic.
This is a large set of radio letters to Gaelic learners in clear Gaelic. If you are not up to understanding the letter without help you should [go to LearnGaelic.scot. There you can read and listen at the same time. As far as I know, this is the simplest and clearest continuous Gaelic available, except for what is aimed at kids.