What exactly does "sell on" mean?

[BenDover23]

[Beeesneees]

sold on - resold (usually at a profit)
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[Ivo]

sell on = persuade

Couldn't I sell you on one more coffee? ≈ Really, do you not drink more a cup of coffee?

Is the director completely sold on the idea of combining the two firms? ≈ Director already quite persuaded to merger two firms.

[Beeesneees]

'Sell on' does not mean persuade in Ben's passage. In Ben's passage something is sold on, rather than someone being sold on something.

Where 'sell on' means something like 'persuade', it is actually ' find the idea acceptable'. Sometimes you can use 'persuade' Most times you cannot. Because of this your first example doesn't work anyway.

Is he sold on something? = Does he find the idea acceptable?

These discussions of the many uses for the phrases which I don't usually even have to think about when I use them are what makes this website so interesting.
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