Snoop

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mid 19th century: from Dutch snœpen ‘eat on the sly’.

wiktionary

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From Dutch snoepen(“to pry, eat in secret, sneak”). Related to Dutch and Low German snappen(“to bite, seize”), Dutch snavel(“beak, bill, pecker, neb”), German Schnabel(“beak, bill, mouth”). More at snap.

etymonline

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snoop (v.)

1832, "to go around in a prying manner," American English, probably from Dutch snoepen "to pry," also "eat in secret, eat sweets, sneak," probably related to snappen "to bite, snatch" (see snap (v.)). Specific meaning "to pry into other people's business" is attested from 1921. Related: Snooped; snooping.

snoop (n.)

1891, "act of snooping," from snoop (v.). Meaning "one who snoops" is from 1929; meaning "detective" is from 1942. snooper "one who pries or peeps" is from 1889.