for all intensive purposes

We’ve previously explored the idiosyncratic contextualisation and substitution of a word or phrase to something more familiar or plausible in the speaker’s own experience termed an eggcorn and liked revisiting the concept with more examples, including a growing database of citations.
A whetstone does not lubricate a dull blade but rather gritty and sharpens it and hence the often mistaken idiom “to whet one’s appetite”—one wonders what else might be properly described as such when one understands wet. A penthouse apartment derives from the Anglo-Norman pentiz and ultimately traced to the Latin appendō for something I attach and was originally referring to something akin to an outhouse and through eggcornisation and folk etymology the suite appended to the top of a building was understood to be a compound form of house.