the.com/guerrilla

means An irregular fighter who uses ambush, sabotage, and hit-and-run tactics rather than open battle, typically against a larger conventional force.

from Spanish for 'little war' — guerra means war, and the diminutive -illa shrinks it down. The word rose to fame during the Spanish resistance against Napoleon's occupying army in the early 1800s, when small bands of Spanish fighters harassed the much larger French forces instead of meeting them in open combat. The tactic got the name 'little war,' and the fighters themselves eventually inherited the word as a noun — a guerrilla being someone who wages one.