What's (something) in aid of?

British & Australian, informal

something that you say when you want to know why someone has done something.

I heard the shouting from the other side of the building. What was that in aid of?

A present! What's this in aid of?

• here's to
• here's to someone
• here today, gone tomorrow
• here you go
• He wasn't born yesterday!
• He who pays the piper calls the tune.
• hidden agenda
• hide a multitude of sins
• hide head in the sand
• hide light under a bushel
• hide your head in the sand
• hide your light under a bushel
• high and mighty
• highest rung on the ladder
• high-flier
• high ground
• high jinks
• highly-strung
• high roller
• highways and byways
• hinge on
• hinge on something
• history in the making
• hit a brick wall
• hit a home run