Does anyone recognize this? It’s not ringing a bell, and the authors don’t footnote their source.
Though the book was published in 1930, the manuscript would have been completed in 1928 or 1929. In an addendum (p. 273), the authors make reference to a new edition of Alexander A and B by F.P. Magoun, published in 1929, “too late to be considered in the present volume”. This suggests that any work by Tolkien to which they could have had access must have been published, at the latest, by early 1929. That leaves a relatively short list.
- A Middle English Vocabulary (1922)
- “Philology: General Works.” The Year’s Work in English Studies 4 (1923) 
- “The Devil’s Coach-Horses.” The Review of English Studies 1.3 (July 1925)
- Sir Gawain and the Green Knight. Ed. J.R.R. Tolkien and E.V. Gordon (1925)
- “Some Contributions to Middle-English Lexicography.” The Review of English Studies 1.2 (April 1925)
- “Philology: General Works.” The Year’s Work in English Studies 5 (1924) 
- “Philology: General Works.” The Year’s Work in English Studies 6 (1925) 
- “Foreword.” In Walter E. Haigh’s A New Glossary of the Dialect of the Huddersfield District (1928)
- “Ancrene Wisse and Hali Meiðhad.” Essays and Studies by Members of the English Association 14 (January 1929)
The passage in question could be from Tolkien and Gordon’s edition of Sir Gawain and the Green Knight, because the authors do cite that edition, but they normally refer to Tolkien and Gordon together (e.g., pp. 73, 257, 266, 267). There is one instance where they refer to this text by Tolkien’s name alone (p. 17), so the passage quoted above could be from Sir Gawain. But I don’t remember it and didn’t spot it at a glance. There are sections of Tolkien’s review essays for YWES discussing place-names, but at a quick glance, I didn’t see the quoted passage their either. Likewise, I scanned through his other works of the period and didn’t come across it. Some of these works I know pretty well, and I don’t recall this passage. It’s certainly possible I missed it in hasty skimming.
Anyone? And if we can’t track it down, what does that mean? That the authors err in attributing the remarks to Tolkien? Or could they be quoting a statement Tolkien made privately? Or what? If any of you reading this can track down the passage, please do tell.
Update: Utúvienyes and eureka! I’ve found it! See the comments. :)