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The adjective sentimental is from the noun sentiment and the suffix -al, forming adjectives with the sense: of, or relating to, that which is denoted by the first element (cf., for example, the adjective global). The primary meaning of the adjective sentimental, therefore, is: pertaining to sentiment, i.e., arising from, or determined by, sentiment rather than reason.
The adjective sentimental was borrowed into French in a translation of A Sentimental Journey through France and Italy. By Mr. Yorick (London: Printed for T. Becket and P. A. De Hondt, 1768), by the Irish novelist Laurence Sterne (1713-1768).
The title of this translation, by the French man of letters Joseph-Pierre Frenais (17..-1788), is: Voyage sentimental, par M. Stern [sic], sous le nom d’Yorick, traduit de l’Anglois par M. Frénais (Amsterdam: Chez Marc-Michel Rey; Paris: Chez Gauguery. 1769).
In Avertissement du traducteur [pages v & vi], Joseph-Pierre Frenais explained the following about “le titre de Voyage Sentimental”:
Le mot Anglois Sentimental n’a pu se rendre en François par aucune expression qui pût y répondre, & on l’a laissé subsister. Peut-être trouvera-t-on en lisant qu’il mériteroit de passer dans notre langue.
translation:
The English word sentimental could not be rendered by any expression that could answer to it, and it has been preserved. Perhaps will it be found when reading that it would deserve to pass into our language.
The following also mentions the fact that sentimental was a new word in French—it is from a review of Voyage sentimental, published in the Mercure de France, dédié au Roi. Par une société de gens de lettres (Paris: Chez Lacombe) of August 1769 [pages 71 & 72]:
Voyage sentimental. Ce titre ne peut se traduire en françois d’une maniere satisfaisante ; l’auteur est né sensible, & se propose moins de rendre compte de ce qu’il voit que des sensations que les objets lui font éprouver.
translation:
Sentimental Journey. This title cannot translate into French in a satisfactory manner; the author was born sensitive, and proposes less to give an account of what he sees than of the sensations that the objects make him experience.
word histories 
Very interesting, thank you! I wouldn’t have guessed that this word was borrowed in that direction.
One correction: in the second quotation, French “sensible” should be translated as “sensitive”, not as English “sensible”. The meaning is that the author keenly senses things — not that he is well endowed with common sense, as English “sensible” would mean.
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Thank you.
I’ve amended the text accordingly.
When I was translating the French text, I first wrote “sensitive”, then I realised that “sensible” was used (at least in the past) in the sense: “endowed with the faculty of sensation”.
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Yeah I agree, it’s likely that English contemporaries of that text (in 1769) might have translated it with “sensible”. But I think I haven’t seen it used with that meaning in any English text from the last century or so; it seems to be completely gone from present-day English.
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The 1996 film “Ridicule” by Patrice Leconte demonstrates Voltaire’s problem with the word “humour”. A marquis at the court of Louis XVI in Versaille tells courtiers about his encounter with “humour” in England.
« Baron, comment avez-vous trouvé les Anglais ? »
« Très distrayants, ils ont une forme de conversation appelée humour, qui fait beaucoup rire tout le monde. »
« Humour…Est-ce comme l’esprit ? »
« Non, pas vraiment »
« Mais alors comment le traduisez-vous ? »
« Et bien, je ne peux pas. Nous n’avons pas de mot pour cela en France ».
Much later, two aristos are exiled in England. It’s a windy day in 1794 on the cliffs from where you can see France on a clear day. The wind blows the hat of the Marquis de Bellegarde [Jean Rochefort] away over the sea.
“My hat! I’ve lost my hat” [subtitle]
“Better your hat than your head” [subtitle], says his companion.
After a moment of reflection Bellegarde says, “Ah… l’humour… l’humour… il est merveilleux.”
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Interesting. Thank you.
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