Is there a word for pant sleeves? I know that 'sleeves' is used for sweaters, but what about pants? I don't think the phrase 'sleeve pants' is idiomatic. Is it? By pant sleeves, I obviously mean the part that covers the entire leg.
They're called legs as well, more specifically trouser legs or pant legs:
a cloth covering consisting of the part of a pair of trousers that covers a person's leg
Which one you should use depends on the continent; the clothing is usually called trousers in the UK and pants in the US, so given your question you should go with pant legs.
Back in Tudor times sleeves were separate items, particularly for women's dresses. They would be held on on with ribbons or buttons. So a particular word came about. At that time, pants didn't even exist. The modern-day trousers as middle class dress didn't really come about until sometime around the 18th century. Breeches would have been formal dress before then.The separate leg covering word you are looking for is "hose", knitted stockings that would cover the leg while the breeches stopped at the thigh (Tudor era) or, later on, the knee.