Merriam-Webster's Collegiate® Dictionary, 11th Edition
COUGH
I. verb
Etymology: Middle English, from Old English *cohhian; akin to Middle High German kūchen to breathe heavily
Date: 14th century
intransitive verb to expel air from the lungs suddenly with an explosive noise, to make a noise like that of coughing, transitive verb to expel by coughing,
II. noun
Date: 14th century
a condition marked by repeated or frequent coughing, an act or sound of coughing