From the Renaissance practice of singing in four parts:
The melody is called tenore = the holding one
Below the tenore as a basement we have the basso = the deep one
Above the tenore there is the alto = the high one
Above the alto an even higher voice was introduced: the soprano = the uppermost one.
In most dictionaries contralto is given as a synonyme to alto, or alto as shortened form of contralto [?].
The contratenore, higher than tenore, is the male singing alto, mostly falsetto.
So by the use of the presyllable contra for higher than ... I think that the contralto is used for a range near the mezzosoprano.
In Renaissance church music only male singers were used. It wasn't difficult to find some countertenors for singing the alto, but impossible to find adult male sopranoes. So boys before the voicebreak were used, and to preserve their high range they were often castrated in young years [!].
Recommended book about this practice: Alteration / by Kingsley Amis.

Wilfried