Play fast and loose with X has been around a long time; it goes back to at least the 16th century. Robert Nares' magnificently titled A Glossary; or, Collection of Words, Phrases, Names, and Allusions to Customs, Proverbs, Etc., Which Have Been Thought to Require Illustration in the Works of English Authors, Particularly Shakespeare and His Contemporaries, 1822†, derives it from
A cheating game, whereby gipsies and other vagrants beguiled the common people of their money. It is said to be still used by low sharpers and is called pricking at the belt, or girdle. It is thus described: ‘A leathern belt is made up into a number of intricate folds and placed edgewise upon a table. One of the folds is made to resemble the middle of the girdle, so that whosoever should thrust a skewer into it would think he held it fast to the table; whereas, when he has so done, the person with whom he plays may take hold of both ends and draw it away.’ —Sir J. Hawkins, [note on ‘Like a right gipsey, hath, at fast and loose, Beguil’d me to the very heart of loss.’ - Ant. & Cleo., IV, xii, 28.
In other words, you think you've got it pinned down, but you're wrong.
† But I don't actually know that what follows is from that edition; this is quoted from Furness' New Variorum edition of KJ. I consulted A New Edition, with Considerable Additions Both of Words and Examples, by James O. Halliwell, Esq., F.R.S., &c., and Thomas Wright, Esq., M.A., F.S.A. 1858, and found a somewhat longer version there.