The Collaborative International Dictionary of English v.0.48:

Ecchymosis \Ec`chy*mo"sis\, n.; pl. Ecchymoses. [NL., fr. Gr.
   ?, fr. ? to extravasate; 'ek out of + ? to pour.] (Med.)
   A livid or black and blue spot, produced by the extravasation
   or effusion of blood into the areolar tissue from a
   contusion.
   [1913 Webster]