[Spellyans] musyn

[Craig Weatherhill]

"musyn" is a place-name element I've come across several times, in  
names such as Porthmissen near Padstow.

This was ; Portmusyn 1355; Porthmusyn 1396, Pormusyn 1471; Porthmewsan  
1585; Permeson 1702; Permizen Bay c. 1830.

In this, and at least one other name, this appears to be a stream name  
and I believe that it also occurs in West Penwith, where there is an  
offshore rock called Miesem, apparently associated with an offshore  
current known as Froze Muzzam.

Would anyone have an inkling of what this word means?  Its usage tends  
to suggest that it is applied to something that flows.
--
Craig Weatherhill