Originates from Blizzard's game Starcraft where zerg were one of 3 playable races, aliens
like appeareance, zerg were characterized by using large numbers of weak units to swarm the enemy, also another charasteristic of zerg were that everything was organic, ie, zerg didnt used machines or any artifacts, they would mutate their own buildings from special kind of larvae and advanced units were created by mutating
basic ones. Units were cheap to make and it was possible to make extreme numbers in short
period of
time.
Nowadays term zerg is used in
mmo games to describe force consisted of large group of lower level players (often with only
basic equipment) who use numbers rather then strategy to defeat the enemy, therefore requiring no skill. This tactics is commonly known as zerging