The phrase damp squib denotes something intended, but failing, to impress.

A squib is a small firework that burns with a hissing sound before exploding; if damp, it will fail to work.

The earliest instance of damp squib that I have found is from The Morning Post (London) of Wednesday 1^st March 1837:

Mr. Grote¹ is a nice man. We rather like Mr. Grote. To be sure the people in the House call him a “quiz,”² but that is no affair of ours. Mr. Grote is a Benthamite³, a sort of interpreter to Jeremy; and, although his hearers may say, with Dangle in The Critic, “Egad, the interpreter is hardest to understand of the two,” still he does his best. Mr. Grote does not vote black white, like piebald Joseph; or fiz [sic] and sputter, after the fashion of a damp squib, like Roebuck⁴; nor pester people with impertinent interference in matters which he does not understand, like Warburton, Hawes, G. F. Young, and such like small deer; but he is useful, like his silver namesakes⁵, in the small-change trade—the cab and omnibus line of political business.

¹ George Grote (1794-1871), English historian and politician
² quiz: here used in its primary sense, i.e.: an odd or eccentric person
³ Benthamite: an adherent of the Benthamic philosophy, i.e., of the philosophical system of Jeremy Bentham (1748-1832), English jurist and writer on law and ethics, who taught that the aim or end of life is happiness, identified by him with pleasure, and that the highest morality is the pursuit of the greatest happiness of the greatest number
⁴ John Arthur Roebuck (1802-79), British politician
⁵ The groat was an English silver coin worth four pence, issued between 1351 and 1662; the fourpence, which was issued from 1836 to 1856, was occasionally called a groat, but the name was neither officially recognised nor commonly used.

The second-earliest occurrence of damp squib that I have found is from The Leeds Intelligencer (Leeds, Yorkshire) of Saturday 27^th August 1842; the following describes the situation in Huddersfield, Yorkshire, after Chartist⁶ riots:

                                                                                                                              Friday, Aug. 26.
This town has resumed its usual business-like appearance, all is quietness and tranquillity; the mills are running as they were wont, and the operatives at their usual work such as it is. The Chartists, however, are represented to be very busy about something, meeting frequently in secret conclave with locked doors, &c., but little is to be apprehended from them now, as like many other ephemerals they appear to have had their day: they have tried a Whig Government, a Tory Government, and they have had resource to “physical force;” all have failed them, and all they can now do is to talk—“Good God! how they will talk”—and print and publish, and be as far from obtaining their six revolutionizing points as the first day they broached them: they will go out like a damp squib, with more stench than brilliancy.

⁶ Chartism was a parliamentary reform movement of 1837-48, the principles of which were set out in a manifesto called The People’s Charter, which called for six reforms: universal suffrage for men, equal electoral districts, voting by secret ballot, abolition of property qualifications for MPs, payment of MPs, and annual general elections.

The equivalent French expression is pétard mouillé. The earliest instance that I have found is from L’Amitié (Friendship), the preface by Étienne Carjat to Le Diable à Quatre: revue de l’année 1868 en deux actes et quatre tableaux (The Devil between Four: review of the year 1868 in two acts and four scenes – Paris, 1869), by Marcilly, Delafontaine and Marcel—here, the phrase faire le diable à quatre (literally to make the devil between four [persons]) means to exert oneself:

Par ces temps d’orgie et de honteux trafic,
Où des cœurs de vingt ans sont morts avant de battre
Il vaut mieux, après tout, faire le Diable à Quatre,
Dût la pièce rater comme un pétard mouillé,
Que d’aller bêtement, d’un poumon éraillé,
Mêler sa fausse voix à la lugubre antienne
Que chantent les crevés de l’humour parisienne.
     translation:
In these times of orgy and shameful traffic,
When twenty-year-old hearts have died before beating
It is better, after all, to exert oneself,
Should the play fail like a damp squib,
Than to stupidly, with a hoarse lung,
Mix one’s out-of-tune voice with the lugubrious chant
That the worn-out adepts of Parisian humour sing.