Souvenir used in English to refer to a memory (as in the French)
Boyer, A., The Royal Dictionary Abridged. In two parts. I. French and English. II. English and French (London, 1751), n.p.: Souvenir, S.M. Remembrance, Memory; Se souvenir, V.R. to remember, to call to mind, or have in memory; Se souvenir (impers.) Ex. Il me souvient, I remember; il loi souvient, he remembers.
Boyer, A. The Compleat French Master for Ladies and Gentlemen (17th edition: London, 1753), 217: 'se souvenir to remember'; 223: 'Assurez de mon souvenir. Remember me to him'; 379: 'Je vous prie seulement de vous souvenir de moi, I only desire you to remember me'; 405:' Hors de Vûë, hors de Souvenir. Out of Sight, out of Mind.'
Nugent, Thomas. Travel Through Germany (London, 1768), i.276
Home, Henry (Lord Kames), Elements of Criticism (Edinburgh, 1762), 166 and 195
Letters written by the Late Right Honourable Philip Dormer Stanhope, Earl of Chesterfield, to his Son (London, 1774), ii.240 and 585
The Works of George Lord Lyttelton (Dublin, 1774), 665
Letters supposed to have passed between M. De St. Evermond and Mr. Waller (London, 1770), 155
J. Hawkesworth, The Works of Jonathan Swift, D.D. Dean of St Patrick’s, Dublin, Including the Whole of his Posthumous Pieces, Letters, &c. (London, 1784), viii.254
The elements of the English Language, Explained in a new, easy, and concise Manner, by way of Dialogues / Les Éléments de la Langue Angloise, développés d’une manière nouvelle, facile & très-concise, en forme de Dialogues (London, 1785), 64: 'I will put him in mind of you. Je le serai se souvenir de vous'; 314: 'remember me to him . . . assurez le de mon souvenir'.
Lewis Chambaud, Idioms of the French and English Languages (London, 1793), 131: 'To the best of my remembrance. Autant que je m’en puis souvenir.'
Souvenir used in English to refer to an object
Catalogue Stock in Trade Mr. J. Frankland, Jeweller (n.p. 1776), 7: 'A souvenir mounted in gold.'
James Douglas, Travelling Anecdotes through various parts of Europe (London, 1786), i.41: '. . . the youngest of the two girls . . . asked if she was certain, that the little souvenir she gave her was safe in her pocket.'
The Life of Catharine II. Empress of Russia (third edition: London, 1799), i.182: '. . . the countess [Sophie Auguste Friderique] wrote once more to the empress in 1789, inclosing the lines in her own hand-writing, and delivered it to the care of her nephew, count Augustus von Mellin, president in Riga, who has made himself so famous by his excellent maps of Livonia. Very soon afterwards she was agreeably surprised at receiving, by the hands of count Nesselrode, ambassador from Russia at the court of Berlin, not only an exceedingly fine miniature of the empress, richly set with diamonds, accompanied with a golden souvenir, also set with brilliants, with the cypher E. II. (Ekatarina the second), but also this very gracious letter: . . .'
William Tytler, An Inquiry, historical and critical, into the evidence against Mary Queen of Scots (London, 1790), ii.406 (citing a letter from Mary to ‘son Aumonier’): 'Advisez moy de tout ce que vous penserez pour mon salut par escrit. Je vous envoyeray un dernier petit token. (Souvenir.)'
After about 1800 the word souvenir is commonly used to denote a physical object. The OED cites instances from M. Edgeworth, 'Emilie de Coulanges' in Tales Fashionable Life (1812), v.125 (‘Trifles, which she intended to offer as souvenirs to her English friends’); Stephen Trav. Russia (1839), 75 (‘He gave me his last painting as a souvenir for his sister’); and Charles Dickens, All Year Round, 22 November 1862, 249/2 (‘The walls are decorated with such simple keepsakes and souvenirs of the home-land as I carry about with me’).