hobbyist comes from hobby ('a pursuit done for pleasure', a shortening of hobby-horse) + the agentive suffix -ist. Morphologically, the ending is part of the etymology: the suffix is attached to the older base named in the history, producing a later English derivative. In present English, the noun sense is "a person who pursues an activity for pleasure in their spare time", so the historical development ends in a clearly identifiable modern dictionary use. The same base also appears in related forms such as hobby. Its semantic neighborhood includes amateur, enthusiast, aficionado, and dabbler, which helps locate the modern sense without adding a separate etymological claim. The named historical forms include Middle English hobyn.