Walt Whitman and his (likely) lover Bill Duckett.
The word "homosexual" didn't appear in print until 1869, when a Hungarian writer named Karl-Maria Kertbeny wrote an anonymous pamphlet arguing against a proposed section of the Prussian legal code that would make homosexual acts illegal. Kertenby's close friend had been gay, and he'd committed suicide after an extortionist threatened to expose him. Kertbeny wanted to make sure nothing like that ever happened again.
For much of its history, homosexuality had a language problem. Gay people lived in a world with no words for what they were, where homosexual love wasn't only forbidden but invisible--enciphered in metaphor, perhaps, but never plainly discussed.
We two boys together clinging,
One the other never leaving,
Whitman had his own word for homosexuality: "adhesiveness." He borrowed the term from phrenology: a popular pseudoscience based on the idea that the size and shape of a person's skull said something fundamental about their character. According to your cranial measurements, you could be classified as "adhesive": which meant you were highly prone to same-sex friendships. As science, phrenology was bullshit--but, by linking sexuality to an unalterable fact of physiology, Whitman was making a radical point: he was born this way.