They sell knickers in target. But some of them dont have knickers

I have knickers on me.

who invented the knickers

and why.

There is no specific collective noun for knickers (or for underwear), in which case a suitable general collective noun is used. Some examples are a display of knickers, a package of knickers, a drawer of knickers, etc.

I've seen the term 'an embarrassment of underwear', so 'an embarrassment of knickers' will also work.

Culotte is the french word for 'knickers'.