Be not over righteous nor put on too much wisdom, why shouldest thou die before thy time?
And they when they are changed, they murmur not; why shouldest thou?
And woe be even unto the commendable life of men, if, laying aside mercy, Thou shouldest examine it.
Now, thou art the Just One and the Holy, and shouldest do no iniquity.
shouldest thou reveal but one word of this warning, thy life, and those dear to thee, will be the forfeit.
And if I haste to the worst that can be, why shouldest thou go so slowly to the best?
And the Eagle spake: Arise, thou that healest the sick, thou that shouldest know what is to come, for behold a deluge is at hand.
Be not over much wicked, neither be thou foolish: why shouldest thou die before thy time?
And Laban said unto Jacob, Because thou art my brother, shouldest thou therefore serve me for nought?
He turned very red and spake: Lady, why shouldest thou go, as thy name is, birdalone?
Old English sceal, Northumbrian scule "I owe/he owes, will have to, ought to, must" (infinitive sculan, past tense sceolde), a common Germanic preterite-present verb (along with can, may, will), from Proto-Germanic *skal- (cf. Old Saxon sculan, Old Frisian skil, Old Norse and Swedish skola, Middle Dutch sullen, Old High German solan, German sollen, Gothic skulan "to owe, be under obligation;" related via past tense form to Old English scyld "guilt," German Schuld "guilt, debt;" also Old Norse Skuld, name of one of the Norns), from PIE root *skel- (2) "to be under an obligation."
Ground sense of the Germanic word probably is "I owe," hence "I ought." The sense shifted in Middle English from a notion of "obligation" to include "futurity." Its past tense form has become should (q.v.). Cognates outside Germanic are Lithuanian skeleti "to be guilty," skilti "to get into debt;" Old Prussian skallisnan "duty," skellants "guilty."