What does 'off one's pickle' mean?
In a movie called The Boy, there is a scene where the grocery man talks to the new nanny about the old couple, Mr. Heelshire and Mrs. Heelshire:

"One night, I came out here for a delivery.
I didn't know it at the time, but it was Brahms's birthday or would have been.
And Mrs. Heelshire, she was in the sitting room opening presents with the doll.
And Mr. Heelshire... He was in here...off his pickle."

What exactly does 'off one's pickle' mean? Is it an idiom or slang?

Question

What does 'off one's pickle' mean?
In a movie called The Boy, there is a scene where the grocery man talks to the new nanny about the old couple, Mr. Heelshire and Mrs. Heelshire:

"One night, I came out here for a delivery.
I didn't know it at the time, but it was Brahms's birthday or would have been.
And Mrs. Heelshire, she was in the sitting room opening presents with the doll.
And Mr. Heelshire... He was in here...off his pickle."

What exactly does 'off one's pickle' mean? Is it an idiom or slang?

Answer

As a native (British) English speaker, I have to say I think this is highly idiomatic and, possibly, dialectal. Whilst, upon reading your question, I assumed being "off one's pickle" was a euphemism for being drunk, I was not certain about this and it is not a phrase I am familiar with. I'm not sure I would advise adding this phrase to your English repertoire.

That being said, adding colourful phrases to your speech is a great thing to do and native speakers can often infer the meaning even if they have never heard the phrase before. If you like the phrase being "off one's pickle" then feel free to use it.

Answer

Getting really, really drunk. Source: http://www.urbandictionary.com/define.php?term=off%20my%20pickle