A person who does things in a clumsy, disorganized, or inefficient way; someone who makes frequent mistakes.
From the verb 'bumble' (to move awkwardly, from Middle Dutch 'bombelen' meaning to hum or buzz) plus the agent suffix '-er'. The term evolved from the sound bees make to describe any clumsy motion.
Bumble actually comes from the sound itself—when you say 'bumble,' you're echoing the buzzing noise of a bumblebee, which explains why the word perfectly describes something clumsy and chaotic.
Complete word intelligence in one call. Free tier — 50 lookups/day.