Octothorn vs. Octothorpe: What's the Difference?

(rare) octothorpe, the symbol #.

The symbol (#).

The hash or square symbol (#), used mainly in telephony and computing.

On a push-button telephone. Rumor at the telephone company is that a man named Charles B. Octothorp, wanting to make his name famous, would approach anyone with a Touch-Tone ’phone, stop, and say admiringly, “That’s a mighty handsome octothorp you have there.”