Tonic water contains quinine and that gives it its bitter flavor. 
Quinine is known, among other things, for fighting malaria. 
What I am asking, is: Tonic Water was first created with quinine in
order to help people drink a safe drink and get protected from malaria
(or perhaps another illness) or was it just a matter of personal
taste?

Hello, and thanks for the question

It seems it's all the fault of we Brits who couldn't stand the
conditions out in India. And it seems the quinine was originally added
specifically to prevent disease, but the taste mixed so well with gin
that it caught on big-time.

The Wikipedia entry for Tonic Water (
http://www.wikipedia.org/wiki/Tonic_water )says :
"...quinine was added to the drink as a prophylactic against malaria,
since it was originally intended for consumption in tropical areas of
India and Africa where that disease is endemic."

Here's a quote from THE FANTASTIC HISTORIES OF MUNDANE OBJECTS in an
entry on Tonic Water. (
http://www.lethargytartare.com/wallofphlegm/mengelarants/histories.html
)

"When the British first occupied India there were a great deal of
concern in maintaining a British presence there. Besides occasional
revolts, the British military had the country pinned down. The
greatest concern for these noble warriors was not military resistance
but health conditions. It was hot and mosquitoes were spreading
malaria. The Brits often took to the Gin and water to relieve
themselves of the heat and the inhospitable conditions. It sounds
ridiculous to be making Gin cocktails in the middle of a war zone in
India, but they were also concerned about the quality of the drinking
water. Water was a bit iffy so they used Gin for flavor and to kill
whatever else was in the water. So to combat two great concerns of the
British occupation, the Navy began sending great shipments of a tonic
water that had a special supplement: quinine - a malaria treatment.
The Navy men drank the quinine laced Gin and tonic waters almost
exclusively to quench their thirst and in the meantime helped prevent
and treat malaria. The fascinating endnote to this story is that if
you buy tonic water now, read the ingredients. You will find quinolone
is listed. Quinolone is, obviously, related to the malaria treatment
placed in the water years ago. Tonic water continues to have the
additive because the taste is distinctive and because associated with
the stuff. But don't bet on it saving your ass from malaria because
there's not that much in it.

And here's a quote from a BBC site on the history of Gin and Tonic (
http://www.bbc.co.uk/dna/h2g2/classic/A507908 )
"Gin and Tonics were originally developed to cure malaria. When the
british were in the East they become suseptable to malaria and
eventually found out that Quinine (an ingredient in Tonic Water) was
usefull for getting rid of the disease. Well, as you would probably
expect, drinking Tonic Water by itself is pretty nasty (unless you've
aquired a taste for it) and they had problems getting the British in
the East to drink it. Along comes our friend Gin to be mixed with the
Tonic Water, which not only made drinking it much more pleasant, but
also created an excellent drink that would be remembered from then on,
even if it's relationship to the disease was forgotten.

The wikipedia entry for quinine( http://www.wikipedia.org/wiki/Quinine
) says:
"The quantity of quinine in a glass of modern-day tonic water is a
tiny fraction of that formerly used in treating malaria."

Hope that helps

willie-ga

google search strategy:
"tonic water" history