An archaic or poetic form of 'Jesus' used in older English texts, prayers, and literature.
From Latin 'Iesus,' from Greek 'Iésous,' from Hebrew 'Yeshua.' The -u ending is a Latin nominative case ending preserved in older English devotional writing. This form declined as English spelling standardized.
If you read medieval or Renaissance literature, 'Jesu' appears constantly in prayers and oaths ('Jesu preserve us!'). It's the same person as 'Jesus,' but the -u ending marks it as genuinely old English—a linguistic time capsule.
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