If sites list it as 'Merdin' maybe they have/had some good reason.
Mick says he can't hear a 'd' sound.
Maybe there's some Welsh connection here (we exported Coal miners worldwide). If so there is a Welsh name of Merddyn (=Merlin) which is pronuonced as 'mare thin' (with the 'dd' pronounced as a 'hard' 'th' as in 'this' rather than the soft 'th' in 'thin'.