The word 'stopper' is a transparent English formation built upon the verb 'stop'. The root 'stop' entered English from Old English stoppian, meaning to block or plug an opening, which itself likely has a West Germanic lineage possibly influenced by Latin stuppāre (to stop with tow). The agentive suffix '-er' is one of the most productive in English, directly appended to verbs to create nouns indicating the performer of the action. Thus, the literal logic of 'stopper' is "that which stops," a meaning that has remained consistent from its formation to its modern applications for both people and objects that halt motion or seal openings.

Structure: stop (to cease) + er (agent suffix) - stop: From Old English stoppian (to block up, close), of West Germanic origin. Functions as the core verb root. - er: A native English agent suffix, from Old English -ere, used to form nouns denoting a person or thing that performs an action.