Tolkien And Welsh (Tolkien a Chymraeg): Essays on J.R.R. Tolkien's Use of Welsh in his Legendarium - An Interview With Author Mark T. Hooker
From the product description:- "Tolkien and Welsh provides an overview of J.R.R.Tolkien's use of Welsh in his Legendarium, ranging from the obvious (Gwynfa—the Welsh word for Paradise), to the apparent (Took—a Welsh surname), to the veiled (Gerontius—the Latinizaton of a royal Welsh name), to the hidden (Goldberry—the English calque of a Welsh theonym). Though it is a book by a linguist, it was written for the non-linguist with the goal of making the topic accessible. The unavoidable jargon is explained in a glossary, and the narrative presents an overview of how Welsh influenced Tolkien's story line, as well as his synthetic languages Quenya and Sindarin."