‘Willy’?

[LydiaBennetsUglyBonnet]

Never once heard anyone refer to the PoW as Willy.

Does anyone else think Harry is trying to loosely associate his brother with the word ‘Penis’ 😂

No

No

No

Not having read the book.

But I reckon its an "ironic" nickname, so yes a direct reference to penis rather than a loose association.

I see Harold also as a pisstake pet name.

Just personal nicknames for each other. Harold and Willy.

They are brothers with affectionate nicknames for each other.

Well I wouldn't blame him, but no.

I don’t think so, but it is tedious reading a nickname for someone over and over when it isn’t the name they are known by.
He has not called his brother this nickname in public before, and it seems all so twee and babyish.