By LISP:
(layoutlist) will give you a list of layout names
(command "layout" "r" (nth x (layoutlist)) "-NEWNAME-") will rename layouts, here layout number x
Make a loop the length of your layout list, and rename accordingly.
If you need to grab the layout name from say, a block in each layout, this will take you to layout 'x'
(setvar "ctab" (nth x (layoutlist))) wuill take you to the nth layout in your drawing
Just need to put is all together, ask if you get stuck but that is the basics
Or go here:
https://forums.autodesk.com/t5/autocad-forum/lisp-routine-to-rename-all-the-layouts/td-p/3511636
EDIT
Whoops got this the wrong way round, that was renaming sheets not a adding the sheet name into the drawing
Use the (setvar... part to loop through the sheets, use (nth x (layoutlist)) to get the layout name and then edit the text as you want in the sheet from there, noticing that your sheet name isn't a field but is text?