Throughout my childhood (New Jersey, 1950s), they were dungarees. I don't recall any perjorative connotation, and there certainly were no field hands in our urban community. Also, the term was applied to regular from-the-waist-down-only trousers. Denim trousers with above-the-waist straps and bibs were and are "overalls."

I gradually switched to the usage "blue-jeans" or "jeans" during the 60s. I never used the brand-name "Levis," and in fact have rarely bought that brand. Lees, Wranglers, and various store brands all seem to fit better on my no-ass frame.

As you probably knew before you asked, in the US, the term "pants" is used interchangeably both for underwear and for outer trousers. Pant-TIES are undergarments (women's), and the terms "drawers," "skivvies," "undies," and the brand-name "BVDs" also apply to underpants, of either gender.