Francis Brown et al. discuss the meaning of ברך; one definition includes "saying adieu to."
Francis Brown, Samuel Rolles Driver, and Charles Augustus Briggs, Enhanced Brown-Driver-Briggs Hebrew and English Lexicon (Oxford: Clarendon Press, 1977), 138–139 (Logos ed.)
. . . 5. bless, with the antithetical meaning curse (Thes) from the greeting in departing, saying adieu to, taking leave of; but rather a blessing overdone and so really a curse as in vulgar English as well as in the Shemitic cognates: 1 K 21:10, 13 Jb 1:5, 11; 2:5, 9 ψ 10:3. . . .