'allhallow' originates from Old English, specifically the word 'ealra hālgena mæssedæg', where 'ealra' meant 'all' and 'hālgena' meant 'saints'.

'ealra hālgena mæssedæg' transformed into the Middle English word 'alhalowmesse', and eventually became the modern English word 'allhallow'.

Initially, it meant 'mass day of all saints', but over time it evolved into its current meaning of 'All Saints' Day'.