from
The Collaborative International Dictionary of English v.0.48
Dey \Dey\, n.; pl. {Deys}. [Turk. d[=a]i, 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.
[1913 Webster]