From Middle English mayled; equivalent to mail (“chainmail; spot on a bird's feather”) + -ed.
Meanings
Armoured in, protected by, or made of mail.
[I]n the niches, instead of the effigies of mailed warriors, stood stuffed-out dresses, such as are worn by the fashionables of the day. 1843, Charles Knight, London, volumes 5-6, page 38:
(rare) Resembling the scales of armor.
[…] from blossom of lime to perfumed bloom of acacia — darts the humming-bird, his coat of mailed feathers glowing like a gem. 1888, Frederick Albion Ober, A Boy's Adventures in the West Indies, page 169: