Centuries ago, this revolving, serve-yourself tray was called a dumbwaiter, a term we use today for a small elevator for moving food between floors.
Sometime in the past 100 years, this set of revolving shelves was renamed after the female servant it was designed to replace. (Apparently, Susan was a popular name for a woman at the time.)
But "lazy" does not refer to Susan and her service at all.
Etymologists claim that the adjective pertains to the ease with which guests can rotate the device on its spindle, in a lazy fashion, actually giving Susan a break.
SOURCES: 'The Encyclopedia of Word and Phrase Origins,' by Robert Hendrickson; The World Book Dictionary; Webster's Dictionary; The Random House Dictionary.
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