the.com/suit of mail

means A flexible armor made of interlocking metal rings (or sometimes scales/plates) worn to protect the body from cuts and thrusts.

from "Mail" traces back through Old French "maille" to Latin "macula," meaning a mesh, net-loop, or spot/stitch in a net — the same root that gives us "macula" in the eye. The image is literal: armor made of tiny interlocking loops, like a dense metal net worn as clothing. "Suit" simply joined later, from Old French "suite" (a following, a set of things that go together), to describe the full matching ensemble — hood, shirt, leggings — rather than a single piece. So the phrase quietly describes exactly what it is: a coordinated set of mesh.