As Sarah Fentem, who is a journalist for The Atlantic said so succinctly:

Sure, when said within the confines of a lingerie store, by an older saleswoman with a tape measure around her neck and glasses slipping down her nose, it's fine: "Did you see the black underwire has the matching panty?" But taken out of this context, the word "panty" can be grimace-inducing—and there are a few possible reasons for that.

I've heard several people refer to the word as "infantilizing." The addition of the suffix "-ies" (or in the singular form, "-y" ) converts the word into a diminutive. Literally: "little pants." The suffix puts it in the same category as "booties" and "blankies"—words often associated with small children. In fact, according to the Oxford English Dictionary, the first known use of "panties" is from a 1908 set of instructions for making doll clothes. "The undergarment is ... easily made, for the little waist and panties are cut in one piece." Women, it seems, would rather not shimmy into a garment whose name would also suggest they are shimmying into a pair of knee socks and saddle shoes and handed an oversized lollipop.

The word is a sexual word. If you don't agree, picture your father or grandfather. Now picture him saying "panties." I admire the woman who doesn't shudder.

Why does panties sound sexual? Many arguments could be made, not the least concerning advertising. I have a hunch that the sexualization of the word "panties" is the result of some marketing focus group grasping for a word to run alongside pictures of lingerie models in "tempting" mesh undergarments. One of my male friends suggested its similarity to the word "panting." Another friend, also male, said "panties" sounds so naughty simply because it refers to something so exclusively feminine. While the word "underwear" is strictly asexual, "panties" is not.

Because that's what they are?

whats wrong with calling them panties? would you prefer knickers?

This is one of those things that most people don't seem to even think, let alone care, about while other people really get their knickers in a twist about it

What else would they call them (without me laughing my ass off, knickers? Bbwwaaahhahaa)

OMG. I hate that word. Cringe. It is under wear. One wears it under.

My granddaughter, about 3 yrs. old at the time had just finished her bath. I told her to put on her underwear.

She said, "Papa, I don't wear underwear, I wear panties!"

Well....they are panties...unless I call them "drawers". (Edited to correct typo)

Isn’t that what they are called?

I have never even thought about it. it seems like a very trivial thing. I don't care what anyone calls them.

I would feel hurt, confused, sad, and hopeless.

Just kidding!

That’s what I call them too!

How do I feel about females calling my underwear "boxers"? It's just as benign.

As far as I know there's no negative context for calling female underwear "panties".

Women call them that too ... so ?

How about calling them "knickers"?