The story
From gabapentin + -oid.
Etymology from Wiktionary, CC BY-SA 4.0.
gabapentinoid
Today it means: Any of a class of drugs that are derivatives of the inhibitory neurotransmitter γ-aminobutyric acid (GABA), acting to block the α₂δ subunit (gabapentin receptor) of the voltage-dependent calcium channel. Full definition →