God's holy trousers

What the meaning (and origin) of 'God's holy trousers'?

I am not familiar with this phrase, but I would assume it is along the lines of 'Hell's bells!' or the older 'God's truth' ('Strewth').

It is simply a way of expressing surprise or exasperation, perhaps.

DFG

I little joke, no? Holey trousers.