The food history encyclopedias (including the Larousse Gastronomique) and reference books all describe eclairs but provide little if any details regarding their origin. This probably means the eclair is a product of food evolution. There is some conjecture that perhaps Antonin Careme (1784-1833), a famous pastry chef for French royalty might have created something akin to eclairs. The Oxford English Dictionary traces the term eclair in the English language to 1861 Vanity Fair [magazine]2 Feb 50/1 A Waiter, whereon, stood..a plate of macaroons, eclairs and sponge cake. In French, the word eclair means a flash of lightning.

Eclair. The primary meaning of eclair in French is lightning', and one (not very convincing) explanation advanced for its application to these cream-filled choux-pastry temptations is that it was suggested by the light gleaming from their coating of fondant icing.

---An A-Z of Food and Drink, John Ayto [Oxford University Press:Oxford] 2003 (p. 117)