In TiddlyWiki I want the default new tiddler to start with a field named “origin” that will be populated with the word “apple” and to have some boilerplate text in it. How to do it?
I tried to do it by creating a template or a button using AI, but I couldn’t find a solution. That’s where human intelligence must surpass AI! 
We can give you a working example but if you want to learn find the existing button, clone the tiddler and make modifications.
Here some tips, clone $:/core/ui/Buttons/new-tiddler
Modify, note it uses the actions in $:/core/ui/Actions/new-tiddler so clone that now modify the first button tiddler to use your new button actions.
Now modify the clone of $:/core/ui/Actions/new-tiddler like this;
Note how the tiddler is created with
<$action-sendmessage $message="tm-new-tiddler" tags=<<get-tags>>/>
Read about tm-new-tiddler on tiddlywiki.com it simply allows you to add more field/value pairs.
eg;
<$action-sendmessage $message="tm-new-tiddler" tags=<<get-tags>> origin=apple/>
You can also use text="something"
or text={{boilerplate}}