"The original fusiliers in the British Army were The 7th Foot, Royal
Regiment of Fuzileers raised in 1685. This subsequently became The Royal Fusiliers
(City of London Regiment). The original purpose of this unit was to act
as escort to artillery guns, as well as keeping discipline amongst the
civilian drivers.^[2]
Both a Scots (21st Foot) and Welsh (23rd Foot) regiment also became
fusiliers in the period up to and including 1702 and all three regiments
were distinguished by the wearing of a slightly shorter version of the
Mitred Cap worn by Grenadier companies of all other infantry regiments. A
number of additional infantry regiments were subsequently designated as
fusiliers during the 19th century, but this was simply a historic
distinction without any relationship to special weapons or roles.



In 1865 a distinctive head-dress was authorised for British Army fusilier regiments.^[3] Originally a sealskin cap for other ranks,^[4] this was replaced by a black raccoon skin cap of nine inches in height, according to the 1874 Dress Regulations.^[5] Fusilier officers however wore a taller bearskin like their counterparts in the Foot Guards ^[6] The badge for each regiment was placed at the front of the bear or raccoon skin headdress, and consisted of a stylized flaming grenade, with different emblems placed on the ball of the grenade.



Attached to the various types of fusilier headdress, including the modern beret, is the hackle.
This is a short cut feather plume, the colour or colours of which
varied according to the regiment. Initially, the only regiment
authorised to wear a plume or hackle were the 5th Foot or Northumberland
Fusiliers. The regiment had originally worn a white feather
distinction, authorised in 1824 to commemorate the victory of St Lucia
in 1778 when men of the Fifth Regiment were supposed to have taken white
feathers from the hats of fallen French soldiers. When in 1829 a white
plume was ordered for all line infantry regiments, to preserve the Fifth
(Northumberland) Regiment's emblem, they were authorised to wear a
white plume with a red tip, allegedly to indicate a distinction won in
battle. The Fifth were designated Fusiliers in 1836.



Following the Second Boer War plumes were added to the headgear of all fusilier regiments in recognition of their service in South Africa."

Taken from Wikipedia's article on Fusiliers.