Non sequitur
Etymology
Latin "non sequitur" means "it does not follow," from "sequi," to follow. In logic it is the broad category for any argument whose conclusion is not supported by its premises. In everyday use it also names a remark with no bearing on what came before.
noun phrase · /non-SEK-wih-ter/
A conclusion that does not follow from the premises given for it.
What it names
Flags the gap where an argument leaps from A to B with nothing connecting them.
Example
"She’s a great violinist, so she’ll make a fine accountant" is a non sequitur.
Related idea
A post hoc is a specific non sequitur, wrongly inferring cause from mere sequence.