Raiment, n.
Etymology: [Abbrev. fr. arraiment. See Array.]
1. Clothing in general; vesture; garments; -- usually singular in form, with a collective sense. Living, both food and raiment she supplies. Dryden.
2. An article of dress. [R. or Obs.] Sir P. Sidney.
Shades of meaning
Fernald has no entry of its own for raiment; he lists it under dress.
Where he writes about it:
Clothes, clothing, and garments may be used of inner or outer covering; all the other words in the list (with possible rare exceptions in the case of raiment) refer to the outer garments. — from dress
Array, raiment, and vesture are archaic or poetic; so, too, is habit, except in technical use to denote a lady's riding-dress. — from dress