Safar (صفر) is the second month in the Islamic calendar.
The root of the name, صفر ṣafr, has three basic areas of meaning: 1) whistle, hiss, chirp; 2) be yellow, pale (for humans); 3) to be empty, devoid, vacant. The name of the month likely derives from the color yellow or vacancy.
Read more about Safar: Timing, Islamic Events