"in poor taste," 1888, from earlier sense of "shabby, seedy" (1862), adjectival use of tackey (n.) "ill-fed or neglected horse" (1800), later extended to persons in like condition, "hillbilly, cracker" (1888), of uncertain origin. Related: Tackiness.
The word "tacky" is a Southern colloquialism. It was coined by a wealthier or more refined and educated class for general application to those who were not sheltered by the branches of a family tree, who were "tainted." Those who were wealthy and yet had no great-grandfathers were "tackies." The word was used both in contempt and in derision. It is now nearly obsolete in both senses. There are no aristocrats in the South now, and therefore no "tackies." No man who has the instincts of a gentleman is spoken of as a "tacky," whether he can remember the name of his grandfather's uncle or not. But it has its uses. It is employed in describing persons of low ideas and vulgar manners, whether rich or poor. It may mean an absence of style. In dress, anything that is tawdry is "tacky." A ribbon on the shopkeeper's counter, a curtain in the bolt, a shawl or bonnet, a bolt of cloth fresh from the loom may be "tacky," because it is cheap and yet pretentious. In Louisiana the inferior grade of Creole ponies are known as "tackies." [Horace Ingraham, Charleston, S.C., in American Notes and Queries, Feb. 15, 1890]