bless (v.) Look up bless at Dictionary.com
Old English bletsian, bledsian, Northumbrian bloedsian "to consecrate, make holy, give thanks," from Proto-Germanic *blodison "hallow with blood, mark with blood," from *blotham "blood" (see blood).

Originally a blood sprinkling on pagan altars. This word was chosen in Old English bibles to translate Latin benedicere and Greek eulogein, both of which have a ground sense of "to speak well of, to praise," but were used in Scripture to translate Hebrew brk "to bend (the knee), worship, praise, invoke blessings." Meaning shifted in late Old English toward "pronounce or make happy," by resemblance to unrelated bliss. No cognates in other languages. Related: Blessed; blessing.