Mandarins were first imported into the Mediterranean region from China through the port of Tangiers; it was at this time that the name Tangerine became associated with Mandarins. The name tangerine has no botanical standing and the term is rarely used outside the US. The use of the word appears to have developed as a marketing term.

To put it succinctly, a mandarin is a mandarin and so is a Tangerine.