Crusades
The term "crusade" used in modern historiography at first referred to the wars in the Holy Land beginning in 1095, but the range of events to which the term has been applied has been greatly extended, so that its use can create a misleading impression of coherence, particularly regarding the early Crusades. The term used for the campaign of the First Crusade was "iter" "journey" or "peregrinatio" "pilgrimage". The terminology of crusading remained largely indistinguishable from that of pilgrimage during the 12th century, reflecting the reality of the first century of crusading where not all armed pilgrims fought, and not all who fought had taken the cross. It was not until the late 12th to early 13th centuries that a more specific "language of crusading" emerged. Pope Innocent III used the term "negotium crucis" "affair of the cross" for the Eastern Mediterranean crusade, but was reluctant to apply crusading terminology to the Albigensian crusade. The "Song of the Albigensian Crusade" from about 1213 contains the first recorded vernacular use of the Occitan "crozada". This term was later adopted into French as "croisade" and in English as "crusade". The modern spelling "crusade" dates to c. 1760. Sinibaldo Fieschi (the future pope Innocent IV) used the terms "crux transmarina" for crusades in Outremer against Muslims and "crux cismarina" for crusades in Europe against other enemies of the church. Medieval Armenian term for Crusades — xacˇ‘e˘nkalk‘.
First Crusade
The causes of the Crusades in general, and particularly of the First Crusade, is widely debated among historians. 
While the relative weight or importance of the various factors may be the subject of ongoing disputes, it is clear that the First Crusade came about from a combination of factors in both Europe and the Near East.
Its origin is linked both with the political situation in Catholic Christendom, including the political and social situation in 11th-century Europe, the rise of a reform movement within the papacy, as well as the military's and religious confrontation of Christianity and Islam in the East.