I don't know about English. In spanish we use the term "defensa indirecta" or "protección indirecta", but it does not refer specifically to indirect protection/defence by fork, it could be a threat of any kind that prevents the piece in question to be captured.
For example, after the silly moves 1.e4 d6 2.Nf3 Bg4 3. Bc4 g6 4.Ne5 and the queen is indirectly protected by a mate threat.
After 1.e4 e6 2.d4 d5 3.e5 c5 4.c3 Nc6 5.Nf3 Qb6 6.Bd3, the d4 pawn is indirectly protected by a discovered attack in case it got captured.
And finally, relating back to your specific case: 1.d4 c5 2.dxc5 e6 3.Be3 Qa5+ 4.c3 is another case of indirect protection, this time by means of a fork threat in case of 4...Bxc5?