It's not just squirrels who collect egg corns
An egg corn is a non-standard reshaping of an existing word that, in its new spelling, intuitively makes sense to many users unaware of their error:
Erroneous as it may be, the substitution involved more than just ignorance: an acorn is more or less shaped like an egg; and it is a seed, just like grains of corn. So if you don’t know how _acorn_ is spelled, _egg corn_ actually makes sense.
Incredibly, there is a linguistic category for phrases such as "for all intensive purposes" - and an entire linguistic database of them.
A few of my favorites so far:
38-year-old, mother-of-three Lauren Bays revels in her new body and new leash on life
Her and her elk are low quality people
Proposed Budget of Expenditures with Tax Levy for Physical Year Beginning July 1, 2004