He took on that nickname after the fact, obviously.
On irc, this nickname was first seen 2 days ago.
That is not entirely correct. There is a period after Galileo's discovery called the Maunder Minimum where sunspots "became exceedingly rare", from wikipedia:
The Maunder Minimum (also known as the prolonged sunspot minimum) is the name used for the period roughly spanning 1645 to 1715 by John A. Eddy in a landmark 1976 paper published in Science titled "The Maunder Minimum", when sunspots became exceedingly rare, as noted by solar observers of the time.
So, is it really odd behavior?
The solution of this problem is trivial and is left as an exercise for the reader.