The idea that rather than being dependent upon an expert doing something for you -- like a master Carpenter constructing your house, you take it upon yourself to "do-it-yourself", by "learning how on the job".
(This entry will be supplemented by my discussion in Chapter 7:-- Background Information. )
The Oxford English Dictionary shows that the phrase has a long history, tracing back to 1616. Even William Penn, in 1693, used it. According to Catherine Dean, the phrase "do it yourself" first appeared in print around 1912. Another source [which I have to locate] traces the concept -- "home improvement" -- as leisure activity associated with the introduction of the first "power" tool, the treadle-driven scroll saw, popular during the 1870s and 1880s. But its current meaning evolved in the 20th century, with the big push coming in the post-WW II era.
Sources: Carolyn M. Goldstein, Do It Yourself: Home Improvement in 20th-century America Washington and New York: National Building Museum and Architectural Press, 1998. 109 pages. Review by Catherine Dean; See bibliogrphy in glossary folder; also what can be found on: "Do It Yourself: Home Improvement in 20th-century America." National Building Museum, 401 F St. NW, Washington, DC 20001.