Gian Giacomo Caprotti da Oreno, also called "il Salaino" (or even Salaì, Salaij, Andrea Salai, that is "the little unclean one" i.e. "little devil", in the slang of those times) was Leonardo's adopted son, probably dating from 1490 when he went to him as an apprentice. Salaì was described by Vasari as "a graceful and beautiful youth with fine curly hair, in which Leonardo greatly delighted."
He became the confidential help, and the handy-man of Leonardo, as well as his lover, for about 30 years. Leonardo gave thim the name Salaì because he was, according to Leonardo's words, "thievish, lying, obstinate, greedy".
In spite of this they were together until Leonardo's death in 1519, and Salaì inherited the master's vineyard at Milan.
Salaì's name also appears (crossed out) on the back of an erotic drawing (ca. 1513) by the artist, The Incarnate Angel, at one time in the collection of Queen Victoria.
It is seen as a humorous and revealing take on his major work, St. John the Baptist, also a work and a theme imbued with homoerotic overtones by a number of art critics such as Martin Kemp and James Saslow (Saslow, 1986, passim).
Another erotic work, found on the verso of a foglio in the Atlantic Codex, depicts il Salaino's behind, towards which march several penises on two legs (Augusto Marinoni, in "Io Leonardo", Mondadori, Milano 1974, pp.288, 310).
Some of Leonardo's other works on erotic topics, his drawings of heterosexual human sexual intercourse, were destroyed by a priest who found them after his death.
Though Salaì was always introduced as Leonardo's "pupil", the artistic merit of his work has been a matter of debate.
He is credited with a nude portrait of Lisa del Giocondo, known as Monna Vanna, painted in 1515 under the name of Andrea Salai (see picture here at the left).
The other portrait of Lisa del Giocondo, the Monna Lisa was bequeathed to Salaì by Leonardo.