Waiter

wiktionary

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Late 14th century, "attendant, watchman," agent noun from the verb wait +‎ -er. Sense of "servant who waits at tables" is from late 15th century, originally in reference to household servants; in reference to inns, eating houses, etc., it is attested from 1660s. Feminine form waitress first recorded 1834. [1]

The London Stock Exchange sense harks back to the early days of trading in coffee-shops.

etymonline

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waiter (n.)

late 14c., "attendant, watchman," agent noun from wait (v.). Sense of "attendant at a meal, servant who waits at tables" is from late 15c., originally in reference to household servants; in reference to inns, eating houses, etc., it is attested from 1660s.