Is there a name for the decorative, often scrolled, capital letter of the first word of a book or chapter? See the scrolled “T” icon by my user name for an example.
It’s called a Drop Cap
The first letter of a paragraph that is enlarged to “drop” down two or more lines, as in the next paragraph. Drop caps are often seen at the beginning of novels, where the top of the first letter of the first word lines up with the top of the first sentence and drops down to the four or fifth sentence.
Drop caps can be anything from highly decorative to merely larger than the following text size.
Smashing Magazine: Drop Caps: Historical Use And Current Best Practices With CSS
MagazineDesign.com: Drop Caps and Initial Letters