BEULAH (byū'la, Heb. be‘ûlâh, married). A poetic name for the land of Israel in its future restored condition (Isa.62.4). The word is the feminine passive participle from the verb ba‘al (“to be a lord,” or “to marry”), and hence could almost be translated “lorded” (cf. Isa.54.4-Isa.54.6; 1Pet.3.6).

International Standard Bible Encyclopedia (1915)

A name symbolically applied to Israel: "Thy land (shall be called) Beulah .... thy land shall be married. .... so shall thy sons marry thee" (Isa 62:4 f). In this figure, frequently used since Hosea, the prophet wishes to express the future prosperity of Israel. The land once desolate shall again be populated.