The most usually given source is Glott’s Hop or Glott’s valley – Glott being the personal name of someone who held, or farmed, land hereabouts. This seems to be consistent with ‘-hop’ or ‘-hope’ meaning a side valley or branch off the main one, but the word Glott as a personal name is apparently not recorded elsewhere.
It has been thought that Glott could mean ‘starer’ [as in ‘gloat’] and it would seem that Mike Harding the folk singer thinks it is to do with the number of celtic-style carved staring stone heads which once could be found in this area.
There are categories of name that come from a combination of two old languages. Where Anglo-Norse names are concerned they are known as ‘Grimston hybrids’ and where they derive from Anglo-Saxon-Celtic languages they are known as ‘Bredon hybrids’.
The scholars offer an all-Anglo-Saxon “Side-valley of the Starer” or a Bredon-type hybrid – “Side-valley of the stream called “Glwys” or “Glws” meaning “Grey” or “Silver”.
It is reasonable – especially if the River Etherow (which Glossop Brook joins near the Roman fort at Melandra) had a Welsh name, such as “Teign” meaning “Roarer” (presumably there were rapids where Tintwistle now is, before the Longdendale reservoirs were built). “Etherow” is presumably a Celtic or pre-Celtic name. It crops up often enough in Spain/Portugal.