rivulet vs spate

rivulet

noun
  • A small brook or stream; a streamlet; a gill. 

  • Perizoma affinitatum, a geometrid moth. 

spate

noun
  • A river flood; an overflow or inundation. 

  • A sudden rush or increase. 

How often have the words rivulet and spate occurred in a corpus of books? (source: Google Ngram Viewer )