'To Asamoth' is a verb used in the E2 community to refer to a user removing all (or most) of their writeups because they are unhappy with some aspect of E2. It is a pejorative term, and would not usually be used if a user, for example, removed writeups so that they could be published elsewhere or for some other 'valid' reason.
This practice is named after Asamoth, one of the first users to do this. In the olden days of E2 users could not remove their own writeups to draft, and 'pulling an Asamoth' required a user to blank the text of a writeup, leaving either a blank writeup or a short note. These had to be deleted by the E2 staff, and as many Asamoths were both unannounced and did not involve blanking every writeup, it could take the staff a good long time to hunt down the blanked writeups.
While today users can remove their own writeups, disappearing without leaving a mess, it is still considered a significant act, and a loss to the database. If you are considering leaving E2, you may of course remove your writings, but we would generally ask that you leave them so that future readers can continue to enjoy them. A common compromise chosen by many noders is to have their writeups moved to the everyone account, so that they can remain on E2 without having the original username associated with them.