snoopy

The adjective "snoopy" is a straightforward derivation from the verb "snoop," which emerged in American English around the 1830s. The verb "snoop" itself is likely borrowed from Dutch "snoepen," meaning "to eat on the sly" or "to sneak," capturing the furtive, secretive nature of the action. By adding the adjectival suffix "-y," meaning "characterized by" or "inclined to," the word "snoopy" was formed to describe a person who is habitually prying or inquisitive. This etymological path illustrates how a term for stealthy snacking evolved into a concept for covert investigation and, finally, into a descriptor for an overly curious personality.

The word is a simplex formation derived from the common noun "snoop". It is not productively built from separate, meaningful morphemes in modern English.