Meaning

noun a thin strong lightweight translucent paper used especially for making carbon copies

adjective lacking solidity or strength

adjective not convincing

originThe origin of the adjective is uncertain; it is possibly from flim(-flam) (“(noun) false information presented as true, misinformation, nonsense; poor attempt at deception, confidence trick, pretence; (adjective) frivolous, nonsensical; deceptive; fictitious”) or a metathesis of film (“thin layer of a substance; slender thread”) + -sy (suffix forming adjectives and nouns). The noun and verb are…

Etymology from Wiktionary, CC BY-SA 3.0