With the founding fathers being big on equality and eradicating of all titles of nobility, it is weird that they decided to keep the name "county" for local administrative areas.

I wouldn't go so far as to say that they are big on equality and eradicating all titles of nobility - most of the founding fathers were landed gentry. They wanted to eliminate inherited nobility, sure, but that didn't mean they'd completely eradicate/revolutionize wording

As to your question, sure the term county came from feudal nobility, but it was also a legal subdivision of government that already existed within the colonies that didn't have to do with feudal counts or nobility, so it was just a continuation of colonial government.

This continuity is seen in a lot of examples after all. Louisiana, for instance, calls its counties parishes, Virginia still calls itself the Commonwealth of Virginia, New England is still called New England despite not being a part of the British Empire anymore, etc.