To render sacred, set apart, consecrate. The English word is from the Saxon, and means to make holy: hence hallowed persons, things, places, rites, etc.; hence also the name, power, and dignity God are hallowed, that is, reverenced as holy.
To 'hallow' is either 'to make holy' or 'to regard as holy.' Both meanings are very old. Thus Wyclif translates Joh 17:17 'Halwe thou hem in treuthe,' and De 32:51 'Ye halwide not me amonge the sones of Yreal' (1388. 'Israel'). In the Lord's Prayer (Mt 6:9; Lu 11:2, the only places where 'hallow' occurs in the NT) the meaning is 'regard as sacred.' All the Eng. versions have 'hallowed' in these verses except the Rhemish (Rom. Cath.), which has 'sanctified'; but in the modern editions of this version the change has been made to 'hallowed.'