Why is "bloody" nasty?

As a Yankee I have always been amused by the British usage of “bloody” as an expletive.

On a visit to Scotland I noticed that folks used “fuck” or some grammatical variant in social settings with relative impunity, but say “bloody” and by God you got some loks.

What gives?

Apocryphal comment: I’ve heard the origins of “bloody” stem from an association with female menstruation.

I always thought “bloody” was a contraction or corruption of “By Our Lady” so maybe it is considered blasphemous or something.

Beside the possibly connoting the Virgin Mary, it is also thought that “bloody” may refer to the wounds of Christ on the cross. The now archaic oath “zounds” (or zwounds) is a direct reference to Christ’s stigmata.

Previous thread from a couple of weeks ago: Why is everything “bloody?”

Erm, that’s not the case around here, “fuck” is always considered a stronger expletive that “bloody” in the part of the country I come from. Whatever you do, don’t let your mother here you say “fuck”.