'hallow' originates from Old English, specifically the word 'hāligian' (and related adjective 'hālig'), where 'hālig' meant 'holy' and Proto-Germanic '*hailaz' meant 'whole' or 'uninjured'.

'hallow' changed from Old English forms such as 'hāligian' and Middle English forms like 'halwen'/'hallowen' and eventually became the modern English word 'hallow'.

Initially, it meant 'to make holy; to consecrate', and over time it has retained that core meaning though modern use is often more formal or archaic in everyday speech.