Henever

"Is it Hannover!" used as a term of disbelief, in the context of "Is it Heck!" by my Grandmother (N/W England) could be corruption of Henniver?

What's Henniver?
I suspect that it's far more likely to be a euphemism for "Hell" - as indeed is "heck".

"Genever" in Dutch is pronounced 'henniver' - and refers to Gin a popular recipe for which was from Geneva, another way of spelling of which is "Geneve".

Genever is rather good in the 3 Bottles (Drei Flaschen), Amsterdam. especially the Oude.

L