I know the phase "figure of speech" means a word or phrase used in a nonliteral sense to add rhetorical force to a spoken or written passage. But I don't get the phase when I break it into single words.
What does "figure" mean here?
In general, a 'figure' is a shape or pattern. It is the form of something. For some reason, the online Oxford Dictionaries have indicated the closest general meaning as archaic:
3.4 archaic The external form or shape of a thing.
I usually start with Wiktionary, myself. Wiktionary's entry for 'figure' has some applicable definitions:
The representation of any form, as by drawing, painting, modelling, carving, embroidering, etc.; especially, a representation of the human body
A visible pattern as in wood or cloth.
So it doesn't have to be a person, like the Oxford entries might lead you to believe. Ignore the bit about wood and cloth in 4. Any visible pattern is a figure.
So, if we have a set pattern of words that we say the same way each time, in other words a pattern of speech, that's a figure of speech.
I have been looking for an answer to the same question. Here is my little research
We have a literal meaning and a non-literal meaning
The non-literal meaning is figurative. The words become a symbol for something else beyond the literal meaning, the non-literal one.
Figurative has the sense of using words to paint/draw/sketch/build/ [non-literal meanings].
You could check the two entries below for help.
The Online Etymology Dictionary
figure (n.) c. 1200, "numeral;" mid-13c., "visible appearance of a person;" late 14c., "visible and tangible form of anything," from Old French figure "shape, body; form of a word; figure of speech; symbol, allegory" (10c), from Latin figura "a shape, form, figure; quality, kind, style; figure of speech," in Late Latin "a sketch, drawing," from PIE *dheigh- "to form, build" (see dough).
Collins COBUILD Advanced Learner's English Dictionary
An allegory is a story, poem, or painting in which the characters and events are symbols of something else. Allegories are often moral, religious, or political.
The book is a kind of allegory of Latin American history.