The term "lifehack" is derived (if a term still in its infancy needs derivation) from the technical hacks that programmers and other geeks have set up for themselves to make their lives easier. This usually means methods of organizing data, little utilities to synchronize files, one-off scripts that automate daily tasks, etc. These things are all personal, often suited entirely to the situation and not shared with anyone. The term surfaced when there was a suggestion to share these and see if others could benefit from these "life hacks".

The term, being more generic than the original derivation, was expanded to a broader definition as the meme spread. Today, lifehacks are basically anything that is a solution to an everyday problem, frustration, etc. As a result, we're seeing the term used to describe solutions to getting organized, losing weight, public speaking, doing your professional job better, time management, etc. As such, the current useage probably more accurately reflects the term itself.

"Life" is a generic term we all use to describe pretty much everything other than the thing we're primarily paid for or really dedicated to. We often ask people how work and life are going and mean pretty much everything in that person's "life".

The terms "hack", "hacking" and "hacker" have a long (and troubled) history in the computing and geek communities, particularly within the open source crowds. Like many other truly useful terms, outright definitions are difficult because "hack" is just the right word for the concepts involved. However, according to the Jargon File (typically the authority on the term), the quickest summary is "an appropriate application of ingenuity" to a problem.

Excepted from "What is a LifeHack or Lifehacking?" on the Glass is Too Big

If your hard drive is your outboard brain, you're a lifehacker - someone who loves to tweak your computer for optimum productivity to make it an ally instead of an adversary. Life hacks apply technology creatively, reprogramming your personal workflow to save time and effort. This book serves up 88 of them, outlined step by step and categorized by cost, platform, and level of geekiness. If you're overwired, overwhelmed, or totally tangled in the very technology that is supposed to simplify your life, this book is for you.

Lifehacker: 88 Tech Tricks to Turbocharge Your Day by Gina Trapani

This book isn't a computer user manual, and it isn't a productivity system. It's a mashup of both. It's where you learn to practice big-picture productivity methods on your very own computer desktop. Whether you're a Mac or Windows user, know only enough to get by or are the family tech support geek, there are tricks here for you. Whether or not you've been turbocharging your day with the tips from Gina's first Lifehacker book, you'll feast on this buffet of new shortcuts to make technology your ally instead of your adversary.

Upgrade Your Life: The Lifehacker Guide to Working Smarter, Faster, Better by Gina Trapani