Definify.com
Webster 1913 Edition
Dey
Dey
,Noun.
pl. 
Deys 
(#)
. [Turk. 
dāi
, orig., a maternal uncle, then a friendly title formerly given to middle-aged or old people, especially among the Janizaries; and hence, in Algiers, consecrated at length to the commanding officer of that corps, who frequently became afterward pasha or regent of that province; hence the European misnomer of dey
, as applied to the latter: cf. F. dey
.] The governor of Algiers; – so called before the French conquest in 1830. 
Webster 1828 Edition
Dey
DEY
,Noun.
 Definition 2025
Dey
dey
dey
English
Alternative forms
Noun
dey (plural deys)
Etymology 2
From French dey, from Turkish dayı.
Noun
dey (plural deys)
-  The title given to the ruler of the Regency of Algiers (now Algeria) under the Ottoman Empire.
-  1977, Alistair Horne, A Savage War of Peace, New York Review Books 2006, p. 29:
- the reigning Dey of Algiers (half of whose twenty-eight predecessors are said to have met violent ends) lost his temper with the French consul, struck him in the face with a fly-whisk, and called him ‘a wicked, faithless, idol-worshipping rascal’.
 
 
 -  1977, Alistair Horne, A Savage War of Peace, New York Review Books 2006, p. 29:
 
Etymology 3
Pronoun
dey
- Eye dialect spelling of they, representing African American Vernacular English.
 - Eye dialect spelling of there, representing African American Vernacular English.
 
References
- dey in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913
 - “dey” in Douglas Harper, Online Etymology Dictionary (2001).