"Hock a Loogie" is a slang expression which means to cough loudly and spit out phlegm. It usually precedes a loud noise to clear the throat. The mucus stored in the lungs and throat becomes discomfiting and that’s when one feels the necessity to “hock a loogie.” Not everyone finds it easy to “hock a loogie” but those suffering from some kind of chest infection may have no other alternative but “hock a loogie” without any reservations.
The term loogie or luggie is used to describe the phlegm one spits out while clearing the throat. The origin of the expression "Hock a Loogie" is not very clear but it may have originated from the words “lung booger” which denotes the thick mucous membrane lining the lungs and expelled forcefully through the nose or throat. Boogers or loogies are the sources through which brats try to indulge in indecent acts by spitting out phlegm noisily in front of others.
A person suffering from nasal congestion may sneeze and blow his nose to relieve his discomfort .Similarly someone may “hock a loogie” to relieve himself from the distressing chest congestion. So in this sense the person may “hock a loogie” for purely medical reasons. The accompanying sound and action to “hock a loogie” may be distasteful to the listeners so it is best for the person to cough up clear his chest in the privacy of his wash room. But youngsters may “hock a loogie” purely as a missile to anger and insult their opponents.