from what I have found on the web the Couch name probably came from Sitric Caoch, the

 Norse King of Dublin in 920 A.D., Who was known to have frequently raided the Devon 

and Cornwall areas. I gleaned this from the web so I don't know if its true or not but

 at least its an answer. Maybe one of many

From my gg Grandfather, Henry Wyatt Couch (born 1795 Charleton, Devon) up to today we

 have pronounced the name 'kootch'.

My grandfather was adamant that it should be pronounced this way.

Family legend has it that our family was originally from Cornwall where the name is 

usually pronounced 'kootch'. In Devon we are told the name is usually pronounced 

'kowtch'. also to COUCH well is to lay close and even. 

Possible named after a dab hand. 

http://www.ropecord.com/cordage/biblio/biblliography.PDF