Kind of interesting -- Mellor:

English: habitational name from places in Lancashire, West Yorkshire, and Derbyshire, earlier recorded as Melver, and named from ancient British words that are ancestors of Welsh moel ‘bare’ + bre ‘hill’.

Dictionary of American Family Names, Oxford University Press, ISBN 0-19-508137-4

Mine is the first reasoning (the Latin):

Perna:

Italian: from the female personal name, Latin Perna. See also Perla.

Portuguese: habitational name from any of several places named Perna in Portugal.

Catalan and Portuguese: from perna ‘leg’; possibly a nickname for someone with long legs, or with a deformed or missing leg.

I didn't know about the others!