abbreviation earlier than 1955
DIY is of course an abbreviation of do it yourself, and both terms refer to the carrying out of a task by oneself, especially around the home. The entries for these terms are currently being revised by OED editors. The earliest use of do it yourself as a phrase found so far dates from the nineteenth century (without the later associations with home improvement):
1845 Richard H. Barham Ingoldsby Legends (1905) 288 If it’s business of consequence, Do it yourself!
By 1910, the phrase being used as an adjective:
1910 Popular Science Monthly May 493 At the Boston Tech a method has been in vogue for long that is there deemed highly satisfactory—it is known as the ‘do-it-yourself method’.
But our evidence for the initialism DIY currently goes back only as far as 1955:
1955 Titusville (Pa.) Herald 22 July 8/4 (advt.) DIY means ‘Do It Yourself’ and you can.
1955 Practical Householder Dec. 203/1 A central pool such as a ‘D.I.Y. Club’ from which..tools can be hired is the obvious advantage.
We suspect that earlier evidence for DIY may exist. Can you beat our DIY efforts?
I've found one antedating of some five or six months, and another from the previous year.
Popular Science magazine (Feb 1955 - Vol. 166: No. 2 - Page 283) has a cut-out-and-post coupon has this address:
And better, from a 1954 advert.
The Argus newspaper (Melbourne, Victoria: 1848 - 1956) Friday 5 November 1954 p. 9 advertising:
Can anyone else find something earlier?