Proper English language usage
As time goes by, a language has additions to its trove of phrases and idioms in common use.
Some of these are good additions, some are bad. This site warns about a few bad uses, and gives
a little insight into why the good ones are so good.
The words 'quid pro quo' are actually Latin, not English.
The word 'quid' means this. The word 'pro' means for.
The word 'quo' means that.
So the entire phrase means nothing more than 'this for that'. Pretty simple.
But as we use a language, several idioms, short-cuts, elisions and so on get
into the popular usage. After eight hundred years of using 'this for that',
the phrase was shortened to 'tit for tat'. It is actually a basic tool in
the politician's arsenal. Almost all politics requires prodigious use of
the mechanism we call 'tit for tat'.
Anyway, as English is a wonderfully rich language, we steal items from
many other languages to provide nuance. For instance, the German word for
'pig' is schwein (we spell it 'swine'). To an English speaker, 'swine'
means something completely different than 'pig'. The French word for 'pig'
is porc (we spell it 'pork'). To an English speaker, the word implies
that the pig meat is prepared for cooking and/or eating.
In that same vein, 'quid pro quo' implies that something nefarious went
on during a 'tit for tat'. So a newsman with no scruples will use 'quid pro
quo' to smear a politician when an ordinary old 'tit for tat' would apply.
It is merely an adjustment for nuance. It is always up to the audience
to determine whether bad things happened or an ordinary occurrence went down.