Where does alcohol originally come from and why was it ever invented?I'm am curious to find out because I have a friend in need of treatment.

Alcohol is a naturally occuring substance.

A very common microbe, the yeast Saccharomyces cerevisiae, eats the naturally occurring sugars in fruit or grains and excretes alcohol and carbon dioxide.  This process is called fermentation.  Similar processes occur in the production of both bread and cheese.The juice contained in a bunch of grapes fallen from the vine will naturally ferment due to the yeasts endemic to the vineyard.

Wine and beer are the earliest and most common forms of alcoholic beverages that man 'discovered' and adopted as part of the lifestyle and ritual of early civilisations.

For example, the earliest evidence we yet have of winemaking is found in and around the early city of Chatal Hyuk (in what is modern-day Turkey), dating from the Neolithic B period - about 8,000BC.  This is about the same time as man was learning to make pottery.

Beer and wine particularly, were an important part of early religious ritual and continue to be even today.  In early times, the effects of alcohol were considered to be evidence of having literally taken the God within.

Distilled alcoholic beverages (spirits) came much later, from around the 12th century AD.

A note on parkerlee's answer... The effects of coffee beans have nothing to do with those of alcohol.  Coffee contains caffeine, a stimulant.  Alcohol is a sedative on the nervous system.  They are in fact opposites.