Diakonissa is a Greek title of honor that is used to refer to a deacon's wife. It is derived from diakonos—the Greek word for deacon (literally, "server"). There does not currently seem to be any standard English equivalent, so most English-speaking Orthodox Christians will use the title most common in the old country churches from which their local family or parish finds its origin.
Diakonissa was also the term used in the ancient Church for the order of deaconess, a non-clerical order which saw to the care of women in the community.
In Arabic, a deacon's wife is called Shamassy (derived from Shamas, Arabic for "deacon"). The Slavic tradition generally uses the same word for deacon's wife that is used for a priest's wife: Matushka (Russian), Papadija (Serbian), Panimatushka (Ukrainian), etc.