Everything or anything that: Do whatever you please.
What amount that; the whole of what: Whatever is left over is yours.
No matter what: Whatever happens, we'll meet here tonight.
Which thing or things; what: Whatever does he mean?
What remains and need not be mentioned; what have you: Please bring something to the party-pretzels, crackers, whatever.
Of any number or kind; any: Whatever requests you make will be granted.
All of; the whole of: She applied whatever strength she had left to the task.
Of any kind at all: No campers whatever may use the lake before noon.
Usage Note: Both whatever and what ever may be used in sentences such as Whatever/What ever made her say that? Critics have occasionally objected to the one-word form, but many respected writers have used it. The same is true of the forms whoever, whenever, wherever, and however. In adjectival uses, however, only the one-word form is used: Take whatever (not what ever) books you need.
When a clause beginning with whatever is the subject of a sentence, no comma should be used: Whatever you do is right.
In most other cases, a comma is needed: Whatever you do, don't burn the toast.
When a noun followed by a restrictive clause is preceded by whichever or whatever, it is regarded as incorrect to introduce the clause with that in formal writing: whatever book that you want to look at; one should write instead Whatever book you want to look at will be sent to your office or Whichever book costs less (not that costs less) is fine with us.
First Known Use of WHATEVER: 14th century
Origin 1300–50; Middle English; see what, ever