Two entries with the name Arnold.

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Arnold

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A knight from Cornwall and brother of Sir Gautere.

Arnold and Gautere fought against King Arthur in the tournament at the Castle Perilous.

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Source
Le Morte Darthur | Sir Thomas Malory, 1469-1470

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Arnold

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Layamon names the Earl of Salisbury as Arnold.

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Source
Brut | Layamon, late 12th century to mid-13th century

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