Half-Golems are, despite the name, nothing like the Half-Fiend or Half-Dragon you may be familiar with from Dungeons & Dragons. Instead, a half-golem is a magitek cyborg; a living creature augmented by replacing limbs with artificial limbs animated by magic, and sometimes incorporating other artificial implants for increased armor or stability.
The half-golem as a concept dates all the way back to Advanced Dungeons & Dragons, were a single "half-Flesh Golem" appeared as a unique NPC in the Ravenloft setting. In 3e, the half-golem appeared as a racial template in the Monster Manual 2. This was then followed by a web enhancement detailing further types of half-golem than those listed in the original MM2 entry.
"The Year of Rogue Dragons" trilogy of novels for the Forgotten Realms setting featured a Half-Iron Golem named Dorn Graybrook as their protagonist.
Eberron features the Self-Forged, a prestige class in 3e and a Paragon Path for Artificers in 4e representing a guy so enamored with magitek and constructs that he progressively swaps out more and more of his original fleshy body for an artificial one, ending up as a living construct.