A fitting entry for Election Day, given my cynical rant yesterday about politicians and special interests:
• Eytmology Today from M-W: quid pro quo \kwid-proh-KWOH\
: something given or received for something else

In the 1560s, a quid pro quo was something obtained from an apothecary. That's because when "quid pro quo" (New Latin
for "something for something") was first used in English, it referred to the process of substituting one medicine for another -- intentionally (and sometimes fraudulently) or accidentally. The meaning of the phrase was quickly extended, however, and by 1591 it was being used for more general equivalent exchanges. These days, it often occurs in legal contexts.

• Previous E.T.