What is Vim's feature name for this: # vim:sw=4:ts=4:et:

It's called modeline

:he modeline

If you start editing a new file, and the 'modeline' option is on, a number of lines at the beginning and end of the file are checked for modelines. There are two forms of modelines.

  The first form:   [text]{white}{vi:|vim:|ex:}[white]{options}

 [text]         any text or empty
 {white}        at least one blank character (<Space> or <Tab>)
 {vi:|vim:|ex:} the string "vi:", "vim:" or "ex:"
 [white]        optional white space
 {options}      a list of option settings, separated with white space or ':',
                where each part between ':' is the argument for a ":set"
                command (can be empty)

Add this to $MYVIMRC:

setglobal modeline

It's called modeline. In help it can be found by grepping

helpgrep # vim

If you wish to check whether modeline are active, do set modeline? (if the are it will say modeline, otherwise nomodeline)

To turn them off for certain, add this in your vimrc

:set modelines=0 "number of modelines vim parses
:set nomodeline "turn off parsing