adjuster comes from adjust + -er, from Old French ajoster ('to bring together'), from Vulgar Latin *adiuxtare, from Latin ad- ('to') + iuxta ('near, beside'). Morphologically, the word is transparent: -er is attached to the older base named in the history, so the modern form packages an inherited or borrowed stem inside a later English derivative. In modern use, the noun sense is "a person who settles claims or a device that regulates something", which keeps the etymology connected to the word's present dictionary value rather than treating it as a merely historical label. The wider word family includes related English forms such as adjust, adjustment, adjustable, showing how the same base continues to support neighboring English vocabulary. The principal historical forms in the chain include Old French ajoster, Latin iuxta, which anchor the explanation in named linguistic material.