Rugged Leather is one of the original Leathers from Vanilla World of Warcraft. Rugged Leather can be skinned form creatures between level 39 to 60 (39 to 90 if you are in a Battleground) where the higher level will yield a higher chance to produce Rugged Leather. The best place to farm Rugged Leather would have to be Burning Steppes to skin the Blackrock War Kodos, located just east of Black Tooth Hovel. The Blackrock War Kodos respawns quickly and is easy to slay.
See below for the exact location to farm Rugged Leather in WoW.
Un’Goro Crater (250-300) (level 50-55)
1. Venomhide Ravasaur, Lar’korwi Mate
3. Un’Goro Thunderer, Un’Goro Stomper, Un’Goro Gorilla
4. Plated Stegodon, Elder Diemetradon