Cabinet wear - often called "cabinet friction" applies to coins kept in an unlined wooden coin cabinet for long periods of time. It typically manifests on coins in better states of preservation, by showing up as a slightly duller, perhaps vaguely shiny area, usually on the obverse, as most collectors store their coins reverse side up.
I always used to think it was caused by the coins sliding about when you moved the cabinet, but apparently it really applies to inert coins just kept in the same position for protracted periods of time.
There's a definition here
I don't understand the last sentence of that explanation though, as we still keep coins in wooden cabinets.
ETA: Happy to be corrected on any of the above. Like @Madness I'm also not 100% sure and am employing some inspired guesswork.