rohieb
That seems to be consistent with my own research. The changeset that named these islands initially didn't cite a source at all, and all of the results for "Mossyard Island" on Google seem to be relying on OSM data. However I've found multiple sources for "Garvellan Rocks", e.g.:
* https://labyrinthlocator.org/labyrinth/mossyard-millennium-labyrinth/
* https://www.geograph.org.uk/photo/6614726
* https://bathingwaters.sepa.org.uk/profiles/profile?location=114582
* https://www.facebook.com/groups/stewartrypostcards/posts/1857330875044538/

So I've changed the name accordingly and kept the old names as alt_name in
https://www.openstreetmap.org/changeset/174101905 .