He later mentions "troll-men" as being amongst those driven off by the knights of Dol Amroth.
"...East rode the knights of Dol Amroth driving the enemy before them: troll-men and Variags and orcs that hated the sunlight."
It is commonly assumed by readers that these two references apply to the same group, though there are of course exceptions. There is disagreement on whether they were just large Men who are being compared to Trolls, and thus another group of Southrons (Haradrim), or some sort of crossbreed between the two races. Supporters of the latter interpretation point to the similar terms "half-orcs" and "goblin-men", appearing in the same book (chiefly in the second volume, The Two Towers), and "Orc-men" and "Man-orcs", appearing in later writings (published in Morgoth's Ring) — all applied to the products of Sauron and Saruman's Orc-Man breeding programs. (The interpretation of these terms as referring to specific "breeds", especially with the Uruk-hai, who had Mannish blood, is another source of disagreement.)
In The Lord of the Rings Strategy Battle Game, the Half-Trolls are "Mahûd men" of Far Harad who were altered to the size and strength of the Olog-hai of Sauron. During the end of the Third Age, when Sauron was destroyed, their powers diminished and they too fell into darkness. This information is not canonical.
In The Lord of the Rings: The Battle for Middle-earth II, the Goblin faction has the option to build Half Troll Marauders. In a later expansion pack Half Troll Swordsmen were also made available. This information is also not canonical.