Just a few places where the text_area form helper (or references to it) did not get renamed to textarea:

p. 172

First paragraph after the code sample at the top of the page:

Rails has form helpers for all the different HTML-level form elements. In the
preceding code we use text_field, email_field, and text_area helpers to capture the
customer’s name, email, and address. …

p. 268

First paragraph:

With all of that back-end setup out of the way, we can now make our UI.
We’ll create this in the same way we’ve created other forms in our app,
with the exception of the text area. Instead of using the text_area() form
helper to make a regular HTML textarea tag, we’ll use rich_textarea(), which will
set up the Trix editor for us, enabling the UI part of Action Text.

p. 388

First line of page (line 9 of the code sample as a whole):

  <%= form.text_area :address, :rows => 3, :cols => 40 %>

Last paragraph of page:

You use the text_field() and text_area() helpers (on lines 4 and 9, respectively) to
gather single-line and multiline input fields. You may specify a placeholder,
which will be displayed inside the field until the user provides a value. …

p. 463

text_area() index entry:

text_area() method, 172, 268,
   388