"Sunday bests"?

[Douglas G. Wilson]

>I have a student from Tryon, N.C., who claims that he and his neighbors
>regularly say "wearing their Sunday bests" rather than "Sunday best."  I'm
>also from N.C., though a different part, and I've never heard anyone
>anywhere say this.  Does anyone know if this is an actual usage, or is the
>student merely making an excuse for his bad proofreading?

Google gives six examples of "my sunday bests", and they look genuine to me.

It seems OK to me, although I don't know whether I've heard/read it before
or not.

The "-s" looks to me like the "-s" from (implied/elided) "clothes", as in
"my sweats" = "my sweat clothes", "my grubbies" = "my grubby clothes"
(these I have heard for sure) ... I'm not certain whether "my dress whites"
is analogous (= "my dress white clothes") or not.

-- Doug Wilson