Etymology and Germanic paganism
The modern English language term bless likely derives from the 1225 term blessen, which developed from the Old English blǣdsian (preserved in the Northumbrian dialect around 950 AD). The term also appears in other forms, such as blēdsian or bldsian (before 830 and derived from Proto-Germanic *blōðisōjanan), blētsian from around 725 and blesian from around 1000, all meaning to make sacred or holy by a sacrificial custom in the Anglo-Saxon pagan period, originating in Germanic paganism; to mark with blood. Due to this, the term is related to the term blōd, meaning blood. References to this indigenous practice, Blót, exist in related Icelandic sources.
The modern meaning of the term may have been influenced in translations of the Bible into Old English during the process of Christianization to translate the Latin term benedīcere meaning to "speak well of", resulting in meanings such as to "praise" or "extol" or to speak well of or to wish well.