Orcish

When it is spelled with a lower case "o", "orcish" means "having physical or cultural traits of an orc ." When "Orcish" appears with a capital "O" it means "the language of orcs ."
No other creatures besides orcs speak Orcish as their native tongue, though many who regularly trade with or fight orcs make it a point to learn the language.
Most orcs are illiterate, and the few that are literate usually speak and write Common but a few orcs have taken to writing their mother tongue with Common script. 
While not quite a written language.  Orcish language has a few dozen glyphs that orcs mark landmarks, sign posts or maps.  The glyphs communicate very simple ideas such as "WATER", "GATHERING PLACE", "FOOD", and "DANGER."