In an idle moment, I clicked on a random link to a listicle of ‘First Date Disasters’. One contributor told how he’d quipped that something was ‘(as) funny as hell’. His date replied solemnly, ‘What’s so funny about hell?’.

Linguistically, and whatever your understanding of hell actually is, this is a genuine and intriguing question. Why do we say ‘(as) funny as hell’? I don’t know. There are several discussions on language forums, but none of them come to any firm conclusion. The consensus seems to be that the phrase has drifted from actually describing hell, however people understand it, to being a general intensifier. Searching Google Ngrams for ‘*_ADJ as hell’ returns sure, sexy, hot, mad, guilty, black, false, deep, terrible, dark. Sexy certainly doesn’t actually describe hell. 

So where does funny as hell fit in? Google Ngrams is doing strange things, because searching for ‘dark as hell, funny as hell’ shows that funny as hell is far more common than dark as hell, and should be on the list. 

Generally speaking, most people use religious-related words far more loosely than in previous times. But be careful – you never know when you’re going to encounter someone who takes these things Very Seriously.