different between motherhouse vs archabbot

English

mother +? house.

motherhouse (plural motherhouses)

The monastery from which the other 'houses' of a religious order or congregation were (directly or indirectly) founded, often eponymous.
The Cistercian order is called after its motherhouse Cîteaux in Burgundy, where abbot St. Bernard initiated in 1113 the reform of their branch of the Benedictine order, which has its motherhouse at Monte Cassino
The convent which is the seat (and often the above original foundation) of the superior of an order or congregation, and/or on which lower ranking houses (such as priories under an abbot) depend.

Webster's Seventh New Collegiate Dictionary, Springfield, Massachusetts, G.&C. Merriam Co., 1967

arch- +? abbot

archabbot (plural archabbots)

(ecclesiastical) In certain Catholic (notably Benedictine) congregations, the title of the general superior, ranking above all other abbots, vested in a particular abbey, which hence is called an archabbey (usually its motherhouse, such as Beuron, which gave its name to a Benedictine congregation).

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