both trompe d'oeil and trompe l'oeil
I have also seen both used interchangeably. However I believe that only "trompe l'oeil" is correct (but am quite willing to be corrected). The verb "tromper" = to deceive and is transitive. You deceive someone, or in this case "the eye"="l'oeil", not "deceive of the eye"="d'oeil". Tromper is often used in the reflexive form "se tromper" = "to deceive oneself" or to be wrong about and then the thing one is wrong about takes "de". "se tromper de route"="to take the wrong road". "tromperie d'oeil"="deception of the eye" might be ok.
Also Larousse online only has the "trompe l'oeil" form.
Rod (who is quite capable of deceiving himself)
PS. Just remembered that "trompe" is also an elephant's trunk, and from the endless song "Un elephant ca trompe, ca trompe" it must also mean trumpet. There must be a pun in there somewhere with "ca trompe"="se trompe".
