I agree with Black Cat - if your link building campaign and internal linking is using anchor text about (buy some pants) - this is what will add value to the page and help it rank better. Just make sure whatever is linking to that page is relevant. also ensure your on-page optimisation is nocely done.

changing the URL's isnt a good idea just for this reason. however, if YOU HAVE to do it, then make sure you use 301 e-direct!