why does the Astrological symbol for Mercury have "Bull horns"?

[.^.]

please explain the signifcance too , if you can, of the cross at the bottom half? is Mercury a combination , perhaps, of Bull thinking and a cross at the bottom? or what maybe was the idea when creating this symbol?

is this symbol for Mercury also used in India ? or where first originated and how changed perhaps?

please explain what you can too about the meaning of the symbols of any other planets used in Astrology and when , where first created and how changed?


thanks for your answers!
Does Taurus have any ties to Mercury?