Well, I read on GarenWeb forums and this pdf article and this pdf article, that the 'Tebow' Mango was in fact named 'Young' (named after Dr. T. W. Young) but for many years the tree was simply labelled "Edward x Kent - no.14." It seems that Pine Island nursery did not know that it was already named so they called it Tebow.
Perhaps, I should start calling my 'Tebow' mangoes, 'Young' mangoes.