One who hampers; a person or thing that hinders or restricts progress.
From hamper + -er (English agent noun suffix). Formed following the productive pattern of adding -er to verbs to create nouns for agents.
Words ending in -er (maker, baker, teacher, hamperer) are among the most productive patterns in English, yet many theoretically possible -er words never actually get used—'hamperer' is grammatically perfect but so rare that most people wouldn't recognize it.
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