A wish, in the form Japanese gives a wish: long life and prosperity, with the verb of wishing left unsaid. That is how Japanese blesses, and it is why the phrase ends on を. It is the standard Japanese for the Vulcan blessing. The wish was Japanese before it was Vulcan. So a person who chooses it for the salute, or for the plain wish under it, gets a real blessing either way. Which they mean is theirs.
It is the wish for a birthday or a new venture, and for the friend who knows the salute.
The English is the Vulcan blessing, first spoken in the Star Trek episode Amok Time in 1967; the two Japanese nouns had stood together as one wish since at least 1746, a Meiji book of English idioms used them in 1898 for the same English words in a stage toast, and who first gave them to a Vulcan in Japanese is not settled.
We want you to be as happy with the meaning as you are with Master Takase's art. To learn more, visit Philology of 長寿と繁栄を.