A falling on or upon; an attack, onset, or assault.
A fall of rain or snow.
The fall of the evening.
To fall on or upon.
Yet, while they were returning to the castle, he failed not to warn Sir Duncan Campbell against the great injury he might sustain by any sudden onfall of an enemy, whereby his horses, cattle, and granaries, might be cut off and consumed, to his great prejudice; wherefore he again strongly conjured him to construct a sconce upon the round hill called Drumsnab, and offered his own friendly services in lining out the same.
A Legend of Montrose
And now this is the last word: here is a horn of oliphant which thou shalt wear about thy neck, Birdalone; and if thou be sore bestead, or thy heart faileth thee, blow in it, yet not before the onfall; and then, whether thou blow much or little, thou shalt be well holpen.
The Water of the Wondrous Isles
For though he knew there would be many a brave onfall and stout bickering, yet, as Sir Lancelot had become the most valiant knight in all the island of Britain, the king had greatly desired that the knight should show how he excelled all the doughty warriors that would come from all parts.
King Arthur’s Knights The Tales Re-told for Boys & Girls
The word ‘onfall’ comes from “on-” + “fall” and is cognate with Dutch ‘aanval’ (“an attack, assault”), German ‘Anfall’ (“an attack, seizure, fit”), and Swedish ‘anfall’ (“an attack, offensive, assault”).