Hammerhead: A coffee drink only served in the USA. It is an American term for a shot of espresso in a coffee cup that is topped up with drip-filtered coffee. As Kris Rosvold explains in the comments: In Oregon, the hammerhead is usually known as a red eye and uses 2 shots of espresso topped up in a 16oz travel mug with drip coffee. It's also sometimes called a "shot in the dark".
The "double-double" is a uniquely Canadian term that is strongly associated with Tim Hortons. It consists of a cup of drip coffee with two creams and two sugars (or double cream, double sugar). The Double-Double coffee will taste exactly the same in any cup size, from the small 10oz cup to the extra large 24oz cup. The chain achieves flavor consistency across cup sizes by employing a pair of countertop vending machines, one dispensing cream and the other dispensing sugar, with a button for each of the four cup sizes. The name "double-double" refers to the number of shots of each added, that is, two shots of cream and two shots of sugar. The terms "single-single" or "regular" and "triple-triple", though not as common as the "double-double", refer to coffee with one shot of sugar and cream and coffee with three shots of sugar and cream, respectively. The machines are calibrated regularly to ensure they dispense a perfect shot of cream or sugar to exacting specifications. The coffee is always poured over the cream and sugar, important to achieve the correct flavor. It is brewed using the pour-over drip brewing method and the coffee maker used is manufactured by Bunn-o-Matic Corporation.
Decaffeinated coffee grew in popularity over the last half of the 20th century, mainly due to health concerns that arose regarding the over-consumption of caffeine. Decaffeinated coffee, sometimes known as "decaf," may be drunk as regular brewed coffee, instant, espresso, or as a mix of regular caffeine beans and decaffeinated beans.
Kelsey Casselbury is a freelance writer and editor based in central Maryland. Her clients have included Livestrong, School Nutrition magazine, What's Up? Media, American Academy of Clinical Chemistry, SmartBrief and more. She has a formal education in personal training/nutrition and a bachelor's degree in journalism from The Pennsylvania State University.