In the north of England "ar" or "arr" is still used for a mark.
And your father, good little Hetty—and Hurry; did they know of your arr'nd?
I don't think you'd come ashore ag'in, on the arr'nd that brought you here afore.
So, ye'll tell me, little Belloni, is arr'bella goin' to marry Mr. Annybody?
Seeing that each looked as implacable as the other, Mrs. Chump called plaintively, "arr'bella!"
Now thin, don't be gaping at the jury, sir; why arrn't you respectful and keep your eye on his lordship?
And ealle uneawas he towyrp on his gecorenum mannum, and arr on him ealle godnysse.
"to growl like a dog," late 15c., imitative. In classical times, the letter R was called littera canina "the dog letter" (Persius).