Dol de Bretagne

A meander forms in a river when the vigorous outer current widens its banks by pushing outwards and the sluggish inner banks narrow by depositing silt. This creates the classic pattern of bends as the river winds its way downstream. In some accounts this is the classic derivation of dol in Dol de Bretagne (Ille et Vilaine); Andel and Dolo (Côtes d'Armor); and even Andouillé (Pays de Loire).

In Welsh, dol signifies a (water-) meadow or flood plain and can be found in hundreds of place names such as Dolygaer, Dol-y-bont, Dolyfelin, Dolffin, Dolblodau, Dolgarrog, Dolbadarn, Dolbenmaen, Dolwen and Dolwyddelen. The meaning includes ‘bend’, ‘turn’ or ‘meander’ and usually refers to the ‘dale’ or ‘valley’ through which a river runs.

This latter sense matches hundreds of place names in Britain such as Arundel, Kendal (Pen-ddol), Annandale, Airedale, Emmerdale, Eskdale, Dalkeith, Dalrymple, Dovedale, Rossendale, Tweeddale and Wensleydale. All of these include the place name element ‘dale’, usually defined in the broader sense of (river) valley.
Some suggest an Old Breton source: (an) dol, ‘(the) meander’ as well as a   Latin one: doliacus. I am a little sceptical about both and suggest that if there is a Breton source its use is almost the same as the Welsh one, indicating a ‘flood plain’ or river meadow .

In Andel the river Gouessant does indeed weave its way around this village; some might say that it is actually surrounded.

Dolo(the ‘o’ comes from the plural form, Doloù) is also encircled:

And the same goes for Dol-de-Bretagne: