Spanish diminutive of 'guerra' (war) — literally 'little war,' coined when Spanish irregulars fought Napoleon's armies.
A member of a small independent group taking part in irregular fighting, typically against larger regular forces; relating to such fighters or tactics.
From Spanish 'guerrilla,' the diminutive of 'guerra' (war), literally meaning 'little war.' The term emerged during the Peninsular War (1807-1814), when Spanish irregular fighters harassed Napoleon's occupying armies. Spanish 'guerra' comes from Frankish *werra (strife, disorder), from Proto-Germanic *werrō (confusion, conflict), the same root that gave English 'war' through Old French 'werre.' So 'guerrilla' is a Spanish diminutive of a Germanic root