Note: E-HAL also has
"A cry used to call hounds out of cover. See Sir H. Dryden's Twici, p. 45"
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from Old French avoi, avoy! of uncertain origin
From: The Canterbury Tales of Chaucer
By Thomas Tyrwhitt, Second Edition, Volume II, 1798
Notes on the Canterbury Tales, P. 499
From: The Works of the English Poets, from Chaucer to Cowper
Edited by Dr. Samuel Johnson, and Alexander Chalmers
Volume I, 1810
The Nonnes Preeste's Tale.