meaning of 'F-able'

Question

I was watching a sitcom and here is this part of the script.

A: Okay so what's the problem?

B: It's...I can't explain it.

A: TRY!

B: It's.... ineffable.

A: I am not "F-able"?

B: No, no, no, no. Ineffable, ineffable means it can't be explained

For your information, A used to be B's girlfriend (B dumped her) and a few years later B wanted to meet her again and they have become a couple again. However, again, B doesn't want to go out with her for some reason and tries to say her that they aren't meant to be or something.

Answer 1

“F-words” can be euphemisms for the word “fuck” and its derivatives. In your example, it expands to “fuckable”, which, given the circumstances, A (wrongly) believes is what B used to describe A, which then implements a comedic device.

Answer 2

F-ing can be used as a milder, toned-down version of a more obscene word

fucking

                                                                           ^{(Mouse over to see word)}

For example, someone might say in an exasperated voice:

Just give me the F-ing hammer, will you?

This would be pronounced as "effing" – and therefore a town like Effingham could easily become a set-up for a lot of jokes, as was done in a suggestive radio skit:

The Effing House Family Restaurant (in Effingham, Illinois)

For lunch, try the huge Effing burger! And what about dinner? Juicy effing steaks...

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The sitcom writers have essentially employed the same humorous device, where effible is being confused with its homophone F-able.