Shakespeare called R the "dog's letter," and here's proof from The Macmillan Spelling Series 5, Teachers' Edition, 1977.

From The Lewis Story Method of Teaching Reading and Spelling Manual, illustrated by Bess Bruce Cleaveland, 1919.

From Recreations for Girls by Lina and Adelia Beard, 1906.

"The five r's of repentance."  From The Instructor, 1961.  [Spoiler: the five r's are: recognition, remorse, resolution, restitution, reformation.]

From P's and Q's: A Book on the Art of Letter Arrangement by Sallie B. Tannahill, 1929.

We're delighted that our One-Letter Words: A Dictionary features prominently in The Irish Times.  Columnist Frank McNally wondered whether our chapter on the letter R included the "great R of our times, the coronavirus reproduction rate":

The viral R is conspicuously absent from one of the more eccentric lexicons on my bookshelf, A Dictionary of One-Letter Words by Craig Conley, published back in 2005, when Sars was the worst health crisis facing the world.

Conley’s entries for the letter instead include the fact that it is a movie rating guide, that it was the old Roman numeral for 80, and that in algebra, it represents “a square upper triangular invertible matrix with positive entries on its diagonal”. Phew. It was also one of several letters with which, in the past, criminals were branded. To be R-rated in that context meant you were a “rogue”.

Under the subheading of “literature”, meanwhile, the dictionary includes a quotation from Daphne du Maurier’s Rebecca, wherein the unnamed narrator finds a book dedicated by her husband to his previous love, the Rebecca of the title and, tearing the page out, throws it into the fire, watching it disappear: “The letter R was the last to go, it twisted in the flame, it curled outwards for a moment, becoming larger than ever. Then it crumpled too; the flame destroyed it. It was not ashes even, it was feathery dust.”

Read in the context of the pandemic, that passage carries an optimistic message. As we look forward to a curve-flattening summer and autumn, we all hope to see the R crumple and disappear. 

Less happily, in the book, the memory of Rebecca haunts the narrator throughout. But on the plus side, I find on looking up the rest of that passage in the original text, that it continues, aptly: “I went and washed my hands in the basin. I felt better, much better.”

Here's an appariton of the letter R frightening an oyster.  From Judy, Or The London Serio-Comic Journal, 1878.

The Shakespeare Papers dedicated an entire issue to one-letter words, and here's one of the pages we contributed.  See our One-Letter Words: A Dictionary.