Eric Patridge, in his Dictionary of Slang and Unconvential English, has:

bless oneself. Ironical for curse: from ca. 1600; coll. After ca. 1800 S.E. 'How my Lord Treasurer did bless himself', Pepys in his diary, April 1, 1665. Also, to bless another: to reprimand, scold, curse at, swear at him: coll. > S.E.; C. 19–20.

Also, the word bless has an interesting etymology: OE blœdsian, blédsian, blétsian 'to bless, wish happiness, or consecrate'. It is cognate with the word blód 'blood' and originally meant something like 'to consecrate or sprinkle with blood'. A cognate verb does not appear in other Germanic languages.

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