Deerstalker cap
A deerstalker cap was a type of 19th century 's cap, designed with a brim on the front and back, with flaps that folded down over the ears. 

Data wore a deerstalker cap as part of his role as Sherlock Holmes in his Sherlock Holmes Program 3A scenario in 2365. ()

An Only boy who lived on  in 2267 wore a deerstalker cap. ()

External link 
 

Clothing