Once in a while

I recently received a note from someone telling me about something she did "every once and awhile."  That's a new one for me, so I looked it up just to be sure I'm not the one who was misunderstanding that idiom.  Now that I think of it, I'm not sure I've ever written the words before today.  Usually, it's a phrase I have said to someone or they have said to me.  (Yes, I know "someone" is singular, and "they" is plural.)  The best summary I found was here.  (I've edited the layout for emphasis.)

This idiom is up there with

• “for all intents and purposes” (NOT “intensive purposes”),
• “hunger pangs” (NOT “pains”), and
• “exacting revenge” (NOT “extracting” it)

for how often it is confused by writers and speakers alike.

Reminder:  "Every once in a while” is the proper form of this expression —

• NOT "every once and a while,” and
• NOT “every once in awhile.”