diaphanous \di-AE-feh-nehs\ (adjective) - Thin and fragile, translucent, filmy or flimsy.
"Jacob's lie was so diaphanous that even his dog could see through it"
From Greek dia- "through" + phainein "to show". The latter underlies "photo-" and "fantasy", borrowed from Greek and itself is derived from Indo-Eropean bhaa- from which French "bouy" and English "beckon", "beacon", "banner", and "berry" (!) are derived via various historical suffixes. This word is usually associated with very thin fabric such as silk which is translucent and flimsy in the original sense. However, the 'flimsiness' in its meaning makes it conducive to a range of colorful metaphoric uses.