welsh promise 

Promise made by a Welshman, or other shady individual, that has no intention of honoring the agreement made by the promise.

Ere mate sort us out with a can of denzel, i'll get you one later yeah?

Sounds like a welsh promise coming from you mate, get it yourself.

welsh promise by BobDole69er September 27, 2013

Welsch promise 

Old Welsch custom of giving a gift of food with one serving missing.
The “Promise” of the gesture was that this gift would not be given if it were not at least good enough for the person giving the gift. The missing serving was presumed to be used to confirm the quality of the item and evaluate possible improvements.
The custom is thought to have originated in the mid-seventeenth century.

We did not understand why our Thanksgiving turkey only had one wing until my grandfather explained the custom of the Welsch promise, and it’s purpose of honoring his guests.

Welsch promise by Juan Moore Beer October 18, 2023