The term "under-the-table" is a modern English compound adjective derived from the literal prepositional phrase. Its figurative meaning, denoting secretive and illicit transactions, relies on the vivid imagery of something being passed beneath a table, hidden from public view. This metaphor draws on the universal concept of the table as a site of open, legitimate business or dining, with the space underneath representing concealment and deceit. The expression solidified in the 20th century, particularly in contexts involving bribery, unofficial payments, or covert agreements intended to circumvent laws or regulations.

This is a fixed compound adjective formed from a prepositional phrase. It cannot be meaningfully segmented into productive morphemes for analysis without losing its idiomatic sense.