peck at vs zerg

peck at

verb
  • To attack with repeatedly soft blows (physically or otherwise) 

  • To unenthusiastically and in small bites. 

zerg

verb
  • To attack an opponent with a large swarm of units before they have been able to build sufficient defences. 

noun
  • A very large group of units or players. 

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