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1550s (implied in sneakish), perhaps from some dialectal survival of Middle English sniken "to creep, crawl" (c.1200), related to Old English snican "to sneak along, creep, crawl," from Proto-Germanic *sneikanan, which is related to the root of snake (n.). Of feelings, suspicions, etc., from 1748. Transitive sense, "to partake of surreptitiously" is from 1883. Related: Sneaking. Sneak-thief first recorded 1859; sneak-preview is from 1938.
"a sneaking person; mean, contemptible fellow," 1640s, from sneak (v.).
To make something smarter and more elegant; enhance; gussy up: and snazzes them up with applique´s/ Install a new loo, or snazz up your current water closet (1970s+)