Moses Mendes (?-1758)
From 18th Century Literary Anecdotes

HAYMAN, the painter, though but an ordinary artist, had some humour.... Mendes, the Jew poet, sat to him for his picture, but requested he would not put it in his show-room, as he wished to keep the matter a secret. However, as Hayman had but little business in portraits, he could not afford to let his new work remain in obscurity, so out it went with the few others that he had to display. A new picture being a rarity in Hayman's room, the first friend that came in took notice of it and asked whose portrait it was? 'Mendes.' 'Good heavens!' said the friend, 'you are wonderfully out of luck here. It has not a trait of his countenance.'

'Why, to tell you the truth,' said the painter, 'he desired it might not be known.'

From Prior, Malone, pp. 405-406.