Etymology of 'éclair'

[The_Physiognomist]

Anyone around these parts know the straight dope on what a tasty, creme-filled dessert has to do with lightning?

[bordelond]

There seems to be no clear answer:

Cincinnati News, Sports and Things to Do | Cincinnati Enquirer

In French, the world eclair means “lightning,” and some people think the pastry was dubbed eclair so that its name would describe the way in which it is meant to be eaten: lightning fast.

http://www.clarionledger.com/news/0105/23/f1.html

No one is sure why the eclair is named for the French word for lightning. Some think that it may be because of the glistening bright icing, while others say it is because it is best served as quick as lightning.

http://forums.egullet.com/index.php?act=Print&client=printer&f=56&t=11290&

And one of our other chefs - formerly of La Tour d’Argent - told us the reason eclairs are called eclairs is because eclair is also the word for lightning and these pastries are so good that they’re eaten as fast as lightning.

http://members.aol.com/oddother/page6.htm

He traces both eclat and eclair to the Indo-European root kell or kla, meaning “to shout, resound, instruct, make clear”, and traces it through the Latin calare, “to proclaim”, to clarus, “clear”. The leap from “clear” to “light, brilliance” is not very great, particularly when clarus can be shown to have traveled as ex, Latin “from” or “out of” + clarus into the French as eclairer, “to lightning”. How “lightning” led to a cream-filled pastry is harder to explain; I envision an early chef finding himself with a tray of uninteresting puff pastry and a bowl of whipped cream or not-quite-set custard left over from an earlier dessert when asked to provide something for unexpected after-dinner guests who’ve dropped by for coffee – voila! in a flash of brilliance, eclairs!

[The_Physiognomist]

Ah, thanks. I did a cursory Google, but couldn’t find anything relevant.

[raygirvan]

From the ones they sell around here, I’d be more inclined to go for a cod etymology using the s-/e- substitution (as in ecole, etoile, etat, etc) therefore eclair = ‘sclair’ from Gk skleros = hard.

[One_And_Only_Wanderers]

also the word ‘clair’ means light as in bleu clair = light blue, as choux pastry is quite light that too could have some bearing.

[clairobscur]

Clair means “light” but only in the visual sense (I should now, with such a nickname), like in your “light blue” example, or in a metaphorical sense (“clear thoughts”). It can’t be used as an opposite of “heavy”, or to refer to something easy to digest.
I’ve no clue about the etymology of “eclair”…