Here is the "definitive" definition of "bloody" from the Oxford English Dictionary:

When used as an adjective:
In foul language, a vague epithet expressing anger, resentment, detestation; but often a mere intensive, esp. with a negative, as 'not a bloody one'. [Prob. from the adv. use in its later phase]
1840 - R. Dana, Bef. Mast., ii. 2, 'You'll find me a bloody rascal. Ibid., xx., 61, 'They've got a man for the mate of that ship, and not a bloody sheep about decks!'

When used as an adverb:
As an intensive . . . exceedingly, abominably, desperately. In general colloquial use from the Restoration to circa 1750; now constantly in the mouths of the lower classes, but by respectable people considered 'a horrid word', on a par with obscene or profane language, and usually printed in the newspapers (in police reports, etc.). [The origin is not quite certain; but there is good reason to think that it was at first a reference to the habits of the 'bloods' or the aristocratic rowdies of the end of the 17th and beginning of the 18th centuries. The phrase 'bloody drunk' was apparently equal to 'as drunk as a blood' (or 'as drunk as a lord'); thence it was extended to kindred expressions, and at length to others; probably, in later times, its associations with bloodshed and murder ('a bloody battle', 'a bloody butcher') have recommended it to the rough classes as a word that appeals to their imagination. We may compare the prevalent craving for impressive or graphic intensives, seen in the use of 'jolly, awfully, terribly, devilish, deuced, damned, ripping, rattling, thumping, stunning, thundering,' etc. There is no ground for the notion that 'bloody', offensive as from associations it now is to ears polite, contains any profane allusion or has connexion to the oath "'s blood!"]