backronym

or bac·ro·nym

[ bak-ruh-nim ]
/ ˈbæk rə nɪm /

noun

an existing word turned into an acronym by creating an apt phrase whose initial letters match the word, as to help remember it or offer a theory of its origin. For example, rap has been said to be a backronym of “rhythm and poetry.”
the phrase itself. For example, “port out, starboard home” is a misleading backronym for posh.

Origin of backronym

First recorded in 1980–85; back1 + acronym
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019