From the phrase "Oh Bust!" which was used when one party would verbally bust on another and the bystander would say "Oh Bust". It has morphed from "Oh Bust" to "Oh Bus" to "Bus" to "Busticle", or "Oh Busticle".
Eli: Oh Busticle!! <pointing and laughing>
2) Adjective/Noun: A word used to describe any emotion, feeling, place, bodypart, object or action, that may be otherwise difficult to name or describe.
2) "I don't know what my problem is," stated Jon, "I must have eaten a busticle."