means A device, substance, or person that keeps something steady, balanced, or unchanging, counteracting unwanted motion, shifting, or chemical breakdown.

from Built from 'stable' — itself from the Latin 'stabilis,' 'firm, steady, fit for standing,' rooted in 'stare,' 'to stand' (the same ancient root that holds up 'stand,' 'statue,' and 'status'). The '-ize' verb ending makes it 'to make stable,' and '-er' names the thing that does the making. So a stabilizer is, quite literally, a 'thing that makes stand firm' — the word doing exactly what it says.