One meaning of the word rhotacism is the phonological process which changes a consonant into a r-sound in certain environments. The consonant affected is usually alveolar and most frequently s or z. The particular realisation of r depends, I suppose, on which language is involved
What got me thinking of this process is my recent efforts to learn some Cornish. The Middle Cornish for “I am” is yth esof vy (ɪθ ˈezə vɪ is the pronunciation I have heard for this). A variation is yth esoma (ɪθ ˈezəmə, I assume, though I have never heard it). In Late Cornish the phrase is th’eroma or th’erof vy. This is a good example of rhotacism.
Then it struck me that in certain parts of the English-speaking world there is a process of reverse rhotacism, whereby r → z. Barry sometimes gets called Baz or Bazza, doesn’t he? And Jeremy, if he is unlucky, may be called Jez or Jezza. I tried to think of more examples, but all I could come up with was soz, which I have occasionally heard for the word sorry. Does Gary ever get called Gaz or Gazza?
It also occurred to me that rhotacism does not appear in SID. I must do something about that, and about lambdacism, but that is a matter for another post.