I confess...

After over 30 yrs on the planet I only just learned that Harry is short for Henry apparently. How the fuck does that work?

Heno maybe. Not Harry. That being short for Harold makes way more sense.

Either way I can't believe I didn't know that.

Henry is originally a French name unlike the Saxon Harold. Henri was anglicised to Harry as phonetically they are not too far apart.

After Macmillan and Wilson we haven't seen too many Harold's around. Loads of Henrys though. Henrys by the dozen and even some Harrys who aren't Henrys.