Her Coworker thought she was making fun of retarded people because she said tardy.

OP said "tardy" and co-worker heard "(re)'tard-y" Not that difficult to understand, but also obviously a silly mistake by the coworker that others should have seen and corrected, instead of punishing OP for their vocabulary.

Even the word retarded is not offensive in its original use. Retarded means to be held back by some force. So even using it to describe people with mental disorders is correct as their mental development has been retarded by a disease or injury. It only offensive when the person using it wants to degrade someone because of their retardation. When people educate themselves about words like this and realize that its only bad in certain contexts the world will be one step closer to being a good place to live.

I believe it's because of the pretentiousness implied with the way the coworker said it. Like she's trying to convince others how tolerant and accepting she is by using buzz words and acting high and mighty for "correcting" the OP.

Because disabled isn't a derogatory term. Saying "differently-abled" is incredibly patronizing and every time someone uses it or the somehow more offensive "handicapable" I'm reminded that just because I can't do things most people can do physically there are some people that assume that I must also have some sort of mental impairment.

Goodbye, cruel world! (shuts door behind you)

Actually, "retard" is the French word meaning "late". Source: I'm bilingual.

Actually, its stems from the Latin tardus, meaning late. That is also the etymology for the French "retard". Also, the pejorative "retard", in English, has this origin too.

Correct me if I'm wrong, but wasn't 'retarded' originally a sensitive, politically correct term? They replaced 'moron', 'imbecile' and 'idiot' with 'developmentally retarded'.

In music there is also retardendo which means to play slowly.

Yes, the root word "retard" literally means slow or to slow down which is why it's used in music as well. And it was politically correct in the past, but people started using it as an insult just like the word "gay"

@51. The pejorative "retarded" comes from the now disused medical classification of Mental Retardation that was itself a replacement for terms such as feeblemindedness , idiocy, etc, which in turn had originally been medical terms that acquired the same pejorative baggage. The implication being that mental development was slower in that individual, just like flame retardant slows the combustion process. The DSM I believe has re-designated the same condition now as 'Intellectual Disability,' more out of political correctness than anything else.

Actually retard means to hold back or slow down. So someone with a mental disorder is being held back from reaching the normal level of mental developement, thus they are mentally retarded. The reason it is in disuse now is the negative conotation recieved from bigoted people who used it as an insult. Infact mentally retarded is the most precise and correct way of describing these people. One just needs to be clear on what they mean by the term.