The set in box. Netheril: Empire of magic also contains the source book The winds of Netheril. On pages 26-28, table 9 lists the year in which almost any AD & D spell has been entered into Netheril. And the table on pages 23-25 lists the original names of the spells.
For example, consider I polymorph. On page 24, we read that his original name was Quantoul's self-love. And on page 26, we see that Quantoul's self-love It was introduced in 1838 NY (-2021 DR).
That said, it is worth noting that when the arcanists of the Netherlands introduced these spells, it is likely that the elves have already had access to some. Quotation of the set in box Cormanthyr: Empire of the Elves (page 124):
… most of the races in Toril took advantage of only the magic granted by their own gods through shamanic and priestly magic. For many centuries, only the dragons and the elves took advantage of the Weaving without divine measure.
Finally, we know that the Nether Scrolls, whose discovery by humans greatly increased their understanding of magic, were written by the sarrukh circa -30000 DR. However, these rolls describe the fundamental magical theory, so the arcanists of the Netherlands had to develop the spells themselves.