When did

Thinking outside of the box

become

Thinking out of the box

???

I’m just saying that those two statements mean very different things. One’s a paradigm shift and the other’s pre-fab thinking. One is invention and cracking the cosmic egg. The other is plug and play.

And yet, the last half dozen or so people I’ve heard use the expression omit the ‘side’ syllable of outside.

Curious.

Has anyone else noticed this?