Definition of "vassalage"

Lord of my love, to whom in vassalageThy merit hath my duty strongly knit

1609, William Shakespeare, “Sonnet 26”, in Shake-speares Sonnets. […], London: By G[eorge] Eld for T[homas] T[horpe] and are to be sold by William Aspley

For all England was his fief, held in vassalage to God and to no man alive, his heart now sang; allwhither his empire spread, opulent in grain and metal and every revenue of the earth, and in stalwart men (his chattels), and in strong orderly cities, where the windows would be adorned with scarlet hangings, and women (with golden hair and red lax lips) would presently admire as King Edward rode slowly by at the head of a resplendent retinue.

2012, James Branch Cabell, Chivalry, page 138