"sordidly parsimonious, stingy," 1560s, from niggard + -ly (1).
It was while giving a speech in Washington, to a very international audience, about the British theft of the Elgin marbles from the Parthenon. I described the attitude of the current British authorities as "niggardly." Nobody said anything, but I privately resolved -- having felt the word hanging in the air a bit -- to say "parsimonious" from then on. [Christopher Hitchens, "The Pernicious Effects of Banning Words," Slate.com, Dec. 4, 2006]
As an adverb, "parsimoniously, grudgingly," from 1520s. Related: Niggardliness.