Contrary to popular lies, this originated in medieval Scotland when, after a full gut of haggis, one could be found swiftly exiting the crannog to clean you're arse due a follow through which has lodged at the rear of the kilt and needs to be scrapped off!
Uch!!! Jean, I must away to the waters edge to clean my fart dart, I shant be long my love!!
when you fart and it doesn't smell right away, but when you move, the fart escapes either a blanket, a baggy pair of pants, etc. The space where the fart hides is called the "fartpartment".
Clay: I accidentally let one slip as i was falling asleep. When i rolled over 20 min later and i got a brief, but intense whiff.
Ruben: It must have been hanging out in the fartpartment