There was a talk given some years ago in March library on local place names,
Friday Bridge is Fridayesbrugg in old english, Frydaybrigge .fridai is the name of a fishery of the monks of Ely in 1086. There was also a Fryday lake in Elm. In Haddenham also was Frydaye weyr, Frydayeware, and near Whittlesey you have Fridaylake.
These probably associated with fishing by the monks for Friday fare as the The Catholic law of abstinence forbids the eating of meat (of mammals and birds). However, fish, shell fish, and all other cold blooded animals may be eaten.