etilqs is backwards for sqlite, which is a database file used by many programs, including firefox
Edit: I found this link which should help, looks like it is firefox Why does Firefox keeps manufacturing etilqs files on my hard drive which tend to be 1-3gb in size? | Firefox Support Forum | Firefox Help
As for whether it is safe to dispose of them, my suggestion would be to cut the files out of the folder and paste them somewhere else for a few days, and see if any of your programs have lost any data / fail to work
If you're happy that all is well, then you can delete the backups you made safely.. From the thread it may be an antivirus issue which prevents firefox from deleting the files, so it may be necessary to add an exclude folder to the av.