I recall a piano teacher once telling me that the tempo marking in a piece I was learning (andante, if memory serves) meant different things in different eras. (Maybe slower in the Baroque than in the Classical eras, again if memory serves.)
I've never been able to keep straight which ones have changed, and what their meanings were in different eras or even to different composers. Wikipedia, for example, mentions that Allegretto is faster now than in the past.
One striking example is that Allegretto hastened as a tempo from the 18th to the 19th century: originally it was just above Andante, instead of just below Allegro as it is now. (Wikipedia)
Which tempo indications are particularly sensitive to era, style, composer, or other consideration? And how so?