Green’s Dictionary of Slang

(US) a French-speaking person.

1857		Borthwick Three Years in Calif. 233: The Frenchman, in his impatience, was constantly asking... ‘Quest ce qu’il dit?’ ‘Qu’est ce qu’il dit?’ This caught the ear of the Americans ... and [in California 1851–54] a ‘Keskydee’ came ... to be a synonym for a ‘Parleyvoo.’ [HDAS].
1945		L. Saxon et al. Gumbo Ya-Ya 175: Creole children [...] refused even to speak French because the others taunted them with the appellation of ‘Kis-kee-dee!’ when they did so [DARE].
1956		H. Gold Man Who Was Not With It 255: They call us Frenchies Kiskeedees because it’s quest-ce qu’il dit, quest-ce qu’il dit all the time [HDAS].
1971		(con. 1850s) W. Carter Ghost Towns 21: The English, Scotch, Irish, and Welsh were accepted [...]; but the French were disliked because they kept to themselves, and became known as ‘Keskydees’ because they kept asking ’Qu’est-ce qu’il dit?’ [DARE].