kjv text for reference > And, behold, one came and said unto him, Good Master, what good thing shall I do, that I may have eternal life? And he said unto him, Why callest thou me good? there is none good but one, that is, God: but if thou wilt enter into life, keep the commandments. He saith unto him, Which? Jesus said, Thou shalt do no murder, Thou shalt not commit adultery, Thou shalt not steal, Thou shalt not bear…
That said, there isn't a whole lot of evidence what is meant here and a rope makes more sense than a camel, because a rich man can become poorer by giving it up just as a rope can be made thinner (by taking away most of the fibers), whereas a camel just can't manage at all.
It wouldn't be too surprising if it was an obscure bit of slang among a less literate group meant for a joke, but there are a few other words that seem to have been coined by gospel writers that have seen lots of litigation, e.g. arsenokoites which seems to echo a construction from Leviticus.