Wax Nostalgic

A very odd usage for the word “wax” is “to become.” So to “wax nostalgic” means to become nostalgic; get wrapped up in thoughts of the past.

I had heard this before, and I understood it from context, but I was curious of the etymology behind that usage of “wax.” I origin is not totally – it goes through Old English and Proto-Germanic and several other origins. I haven’t much heard of any usage other than “wax nostalgic” (I quote another usage below, but it’s odd, and I’ve never heard of any similar usage.)

“Wax” has another off-usage which means “to grow in size” – the moon is known to “wax” and “wane.”