The owner of Timberland, Nathan Swartz was a Ukrainian immigrant who took over a shoe company in Boston, Massachusetts in the 1950s. I wasn't able to find anything about Swartz being a slave owner. According to AFP Fact Check, The Facebook post posted on February 14, 2022, said, "Timberland 'Whip A Ni66a' Hawkins was one of the biggest racist of all time. In fact he owned sooo many slaves during the 1700s he couldn't auction them all off so he would hang them from a tree in his field." The post had an image of a man, but not of Nathan Swartz.
So I'd say this claim is completely false.