byfall

From by- +‎ fall. Compare befall.

byfall (plural byfalls)

1. A falling about; an incidental accessory or accretion; a happenstance; occurrence; instance.
   • 1575, Arthur Golding, Calvin on Psalms:

     The ceremonies are as it were an income or a byfall.

2. A fall of water, usually lesser in size, near to or beside a larger, more predominant waterfall.
   • 1888, William Senior, Near and far:

     There was the small byfall to which I have referred; there was the weir proper; there was a broadish lasher, the whole between them making a very fair description of tumbling bay, flanked by strong, individual streams.