As a wee chap, it was commonplace in our schoolyard for one lad to deride another’s claim or opinion with the phrase, “Get off the grass!”
Naturally I presumed that there was a metaphorical lawn, upon which one’s pronouncements were apt to be exaggerated if not outright falsehoods, or in the case of statements of opinion, extreme and poorly considered.
By reference to this metaphorical lawn, and exhorting the speaker to depart from it, one could indicate one’s poor opinion of the veracity of the speaker’s claims, or of the value of their opinion.
Rather a useful piece of garden topiary, I’m sure you’ll agree!
Ah, the naivete of youth!