Spanner as I know it did not make sense in the context I read it in ("pass me a spanner") so I figured it was a British term for a tool.
1. Chiefly British . a wrench, especially one with fixed jaws. (Web)
1. apparently good or right though lacking real merit;superficially pleasing or plausible: specious arguments. (Web)
This seems to mean plausible and easy to agree with, but in reality false.
"a word that names or signifies something specific: 'Wind' isthe denotation for air in natural motion. 'Poodle' is the denotationfor a certain breed of dog." (www.dictionary.com)
Denotation would appear to be, in essence, the linguistic equivalent of pointing.