Although it is not exactly sure where the expression “Wax poetic” comes from, the term “Wax” started gaining the connotation of writing with too much manner in the 1500’s.
The titular phrase started emerging in the 1800’s, with one of the earliest examples of “Wax poetic” appearing in print occurring in the 5th issue of The Engineer, published in 1858.
“Wax poetic” appeared in print sporadically in the rest of the 19th century, however, it didn’t become widely recognized and used until the 1900’s.
“Wax poetic” grew slowly, with examples restricted to critiques and culturally significant writings, not being endorsed by the masses until the 1980’s, when its appearances in print started rising rapidly.
The prominence of the expression was further increased with the formation of the New York- based trip-hop band, “Wax Poetic”, founded in 1997.
The phrase was first defined on Urban Dictionary on September 19th, 2006, with numerous other entries to follow in the subsequent years.