Sleep tight & other queries

[nfogli@iol.it]

Dear all:

How do you account for the expression “sleep tight – don't let the
bedbugs bite,” from an etymological/contextual point of view? Do you
think it is as frequent now as it was ten or twenty years ago?
I managed to find only the following on the Net:

“It's the bats that keep me awake  Dear Evan: A fellow member of the
Copyediting Digest steered me to your web site when I queried my
cohorts about the origin of "sleep tight." I've looked in several
sources and the best I found was a children's nursery rhyme or song
that included the line "Sleep tight and don't let the bedbugs bite."
I'd appreciate any insight you might have on this phrase. -- Julia
DeGraf, Evanston, IL.

  Bed bugs? Not in my house. When I was growing up, my parents used to
tuck us away with "Sleep tight and don't let the IRS bite." Granted, it
doesn't fit as well as "bedbugs," but it made more sense in our house
and turned out to be sound advice for later life. According to
etymologist Eric Partridge, the catch phrase "sleep tight and don't let
the bedbugs bite" is the American version of a British "children's
goodnight" which differs only in that it specifies "fleas" as the
critters to be avoided. Partridge traced the phrase back to the late
19th or early 20th century, although he speculates that it may actually
be much older, since, he notes, "This is the type of phrase that ...
escapes the attention of lexicographers, even light-hearted ones."
As to where "sleep tight" itself came from, the Oxford English
Dictionary lists "tight" in this sense as a form of the
adverb "tightly," meaning "soundly." Although this "tight" could once
be applied to anything done thoroughly, the OED notes that the only
modern usage is in the phrase "sleep tight."  As a former child myself,
I cannot fail to note the double-edged quality of "sleep tight and
don't let the bedbugs bite" as a bedtime farewell. No one I've ever met
sleeps soundly after having been reminded of bedbugs. I submit that the
phrase is, in fact, probably the diabolical invention of a child, and
(judging by my personal experience), most likely an older sister.”
URL: <http://www.word-detective.com/back-b2.html>"

 I have two more unrelated queries. How many current synonyms of “best-
before date” can you suggest? Are there any regional variations at work
in the use of each?

My other query is whether you are aware of any one adjective (one word)
that means “blissfully ignorant,” or any other equivalent phrase to
express the same idea?

Thank you for any suggestions.

N. Fogli