Definition of "weakly"

I lay in weakly case and confined to my bed for four months before I was able to rise and health returned to me.

1885, Sir Richard Burton, The Book of the Thousand Nights and a Night, Night 18

I'd always been but weakly, / And my baby was just born; / A neighbour minded her by day, / I minded her till morn.

1889, WB Yeats, The Ballad of Moll Magee

"Oh, a huge crab," Jacob murmured—and begins his journey on weakly legs on the sandy bottom.

1922, Virginia Woolf, chapter 1, in Jacob's Room