the.com/crusader

means A participant in one of the medieval military campaigns waged under papal sanction to seize or hold the Holy Land, or more loosely, anyone who throws themselves zealously into a cause they've cast as righteous.

from Traces back to Latin 'crux' (cross), via French 'croisade' and Spanish 'cruzada' — literally 'a marking with the cross,' since participants sewed cloth crosses onto their clothing as a badge of their vow. 'Crusader' itself is an English formation from 'crusade,' which entered the language in the 16th-17th century to describe those earlier medieval campaigns retrospectively — the people living through the actual wars called them simply pilgrimages or holy journeys. The cross on the sleeve was the whole point: it marked the wearer as having taken an oath that was, in theory, impossible to abandon without disgrace.