“What are the origins of the term Sufism?"

Shaykh ‘Abdul Qādir ‘Īsā ash-Shādhilī  ق answered:

There are many different views regarding the etymology (origins) of the word Sufism.

Some say that it comes from the word ṣūfa (a light object that grows on trees used to light fires) because the one who is a Ṣūfī with Allāh is like the ṣūfa that is tossed aside in its submission to Allāh. Other say that it is from the word ṣifa (attribute), for in general it means to adorn one’s self with all lofty traits and to leave all blameworthy traits. Others say it is from ṣafa’ (purity).

Abū al-Fath al-Busti said in his poetry:
The people have disputed and differed regarding the Ṣūfī
Some supposed that it was derived from the word wool (ṣūf)
I would not bestow that name upon anyone save a young man
Who purified himself and was in turn made pure
Untill he was called the one purified (the ṣūfī)

Others said that it from the word ṣuffa, referring to the first generation of adherents to Sufism. Their life of sincere worship was the highest example that the Ṣūfīs sought to follow in all successive generations of Islam. It has been said that is from the word ṣafwa (choice-elect) as stated by Imam al-Qushayrī (ra). It has also been said that it is from the word ṣaff (row), so it is as if their hearts are in the front row with respect to their presence with Allāh  and their hastening to every good act of obedience. Some have said that the word Sufism is derived from the practice of donning ṣūf (coarse woolen garments). It is said that the Ṣūfīs would prefer rough and coarse garments over anything else.

[Adapted from Realities of Sufism by Shaykh ‘Abdul Qādir ‘Īsā ash-Shādhilī ]