"Now, before you dash off and get your YOLO tattoo, let me point out the illogic of that trendy little expression — because you can and should live not merely once, but every day of your life. Rather than You Only Live Once, it should be You Live Only Once ... but because YLOO doesn’t have the same ring, we shrug and decide it doesn’t matter.”
In an essay on slang for the Boston Globe, Ben Zimmer considers YOLO, and quotes English teacher David McCullough Jr. (above, coiner of YLOO — "yaloo"?), as well as the 1748 novel Clarissa, which includes the line "We live but once in this world; and when gone, are gone from it for ever." Okay now the YOLO tattoo.