That is not entirely true. Hindi and Urdu as pure languages are very different languages, and not just because of the script. Hindi originated from Sanskrit, while Urdu borrows from Farsi and perhaps some Arabic.
However, colloquial Hindi and Urdu are somewhat-to-very similar and are indeed intertwined which is what allows most speakers of either language to understand each other.
Give me a word and in most cases I'll be able to tell if it originates from Hindi or Urdu.
precisely. In fact because Urdu is still spoken in parts of India (north & central) AND tends to be the preferred language of scriptwriters & songwriters in Bollywood - a lot of spoken Hindi has picked up a significant Urdu tinge.
However, colloquial Hindi and Urdu are somewhat-to-very similar and are indeed intertwined which is what allows most speakers of either language to understand each other.
Give me a word and in most cases I'll be able to tell if it originates from Hindi or Urdu.