The rhyme is completed with:
GOLDEN EMERODS - while these words may seem unusual, they are the exact words used in the Authorised (King James) Version of the Bible to describe the events of 1 Samuel 6...
What is 'it'?
It's the Ark of the Covenant.
The full context:
At the end of 1 Samuel 4, the Philistines invade Israel and steal the Ark of the Covenant, taking it back home with them to their lands. However, they are then afflicted by a number of punishments and plagues, most notably in 1 Samuel 5v6 where it says, "The hand of the Lord... smote them with emerods."
What are 'emerods'? Well, we know them better today as hemorrhoids! So the Philistines were afflicted with a plague of piles - explaining why in this rhyme they couldn't sit down! How to get rid of them? They had to take the Ark back to Israel - i.e. get it out of town.
But they didn't just send it straight back. After seeking advice from their priests, the Philistine leaders were advised to send the Ark back to Israel accompanied by some statues (or 'images') of mice and emerods made out of gold, as by doing so they believed they could cast out the things that plagued them. (They made five of each, as there were five Philistine leaders - as per 1 Samuel 6v4.)
The tone of this poem reflects the bewilderment that surely must have been felt by the Israelites upon finding their precious Ark returned... along with some golden mice and emerods! To send it back was nice but... what were those guys thinking with these other things?!