Steven Pinker, The Blank Slate: The Modern Denial of Human Nature (Penguin, 2002), p. 11:
Philosophy today gets no respect. Many scientists use the term as a synonym for effete speculation. When my colleague Ned Block told his father that he would major in the subject, his father's reply was "Luft!" — Yiddish for "air." And then there's the joke in which a young man told his mother that he would become a Doctor of Philosophy and she said, "Wonderful! But what kind of disease is philosophy?"
Well, to adapt a chess player's expression, better to make Luft than to make war! (One 'makes Luft' in chess by moving a pawn in front of the castled king's position as prophylaxis against back rank mate. The allusion is to the Vietnam era's 'Make love not war.')
As for 'Doctor of Philosophy,' 'doctor,' etymologically, means teacher (from L. docere, to teach) and 'philosophy' stands in for knowledge or science broadly construed. Thus as late as the 19th century, physicists were still referred to as natural philosophers. 'Ph.D.,' of course, abbreviates Doctor of Philosophy, which is why it is an abomination to see it written as 'PHD.' And when a Ph.D does it it is doubly abominable. But then I'm a linguistic conservative, as well as every other kind of conservative.
In fairness to Pinker, I should point out that after citing the above anecdotes he goes on to say some words in defense of philosophy.
………………….
Addendum: Kevin Spraggett on the importance of making Luft. White to move.