The Old Ones often appears in the writings of Gerald Gardner and Doreen Valiente (who often edited Gerald Gardner’s work). It is clear that in some instances this means the gods of old belief systems. In some cases the use would tend to suggest it could also encompass practitioners of witchcraft who have gone before.
You will also come across “The Old Religion” in the same writing which essentially means pagan witchcraft. “The Old Ways” means the traditions and rituals of Wicca. “The Old Law” forms a section in Gerald Gardner’s Book of Shadows which informs on the “proper” conduct of covens and their members in the opinion of the authors.
Doreen Valiente also makes reference to “the Old-One threefold” in her poem The Door. This is likely the 3 faced goddess Hekate and similar goddesses like Danu.