'Picnic' comes from a shortening of 'pick a nigger.'
'Handicap' came from 'cap in hand,' referring to a disabled person's need to subsist through begging.
The use of the word 'buck' as a slang term for "dollar" derives from a reference to black male slaves.
Crowbars are so named because they were devices used to perform menial labor assigned to blacks.
Jimmies (sprinkles used on ice cream) has a racist origin.
Words and turns of phrase have flowed into the language through a variety of conduits, some less savory than others, resulting in a scattering of everyday words with truly horrifying pedigrees. Additionally, some terms have attracted specious explanations of their origins which paint them as irredeemably offensive when in fact they are perfectly innocuous.