What do we know about words with the spelling -stle? Think of nestle ˈnesl, trestle ˈtresl, wrestle ˈresl. Think of castle, thistle, whistle, epistle, bristle, gristle, jostle, apostle, bustle, hustle, rustle. In all of these the t is silent. There are no exceptions: no words with this spelling in which it is usual to pronounce t. (Compare pistol ˈpɪstl, crystal ˈkrɪstl, etc., with a different spelling.)
So how is it that Neil MacGregor, presenting a BBC R4 series entitled A History of the World in 100 Objects, thinks that the thing that goes with a mortar to grind up grain and spices is a ˈpestl? (You can listen to the programme here, but only for the next few days.)
He is not the only one. Rather reluctantly, I included the -t- form as a secondary variant for pestle in LPD, as do some other dictionaries.
Nevertheless, as the spelling pestle indicates to anyone who is sensitive to this subregularity, it’s usually a ˈpesl . The word rhymes with vessel. Indeed, in the Neil MacGregor programme one of the interviewees, the food writer Madhur Jaffrey, uses the expected pronunciation ˈpesl .
In pre-Gimson editions of EPD you can read DJ’s tactful comment
Note.—The form ˈpesl is usual among those accustomed to make frequent use of a pestle and mortar.
Is this the only case of -stle spelling pronunciation? Or are there people out there who think that Jesus had twelve əˈpɒstlz and that Paul wrote ɪˈpɪstlz?