Adding text depending on clicked button

I made a contact form and put into a popup. That popup then should be triggered from 2 different buttons on the same site. Depending on the clicked button, I want to fill a hidden field with a specific text.

So if I click button 1, the hidden field should be “abc”, if I click button 2, it should be “def”.
Where that specific text comes from, is irrelevant. It can be the id or name of the buttons or even their label.

I was thinking about something like:

[contact-form-7 id="12" title="contact1" myField="abc"]

And put this in the mail template:

[dynamictext dynamicname "CF7_get_custom_field key='myField'"]

But the field remaind empty.