The Assassins called themselves fidaiyun, a term their enemies renamed.

Evidence

“Assassin” was not used by them; it was applied to them by their enemies. The term they used for themselves is fida¯’ı¯, one who is prepared to sacrifice his life for the cause which he serves. This medieval term was revived and used in the 19th century and, more extensively, in the 20th, with approximately the same connotation—those who are prepared to sacrifice their lives in an act of terror and violence in order to promote what they believe to be the true cause of authentic Islam. To the best of my knowledge, the term, in its modern form, first appears in 1859 when it was adopted by a small group of Ottoman conspirators. — Bernard Lewis, From Babel to Dragomans, 576

Categorization

Category: Definitional Content

• DEFINE: Explains the etymology of ‘fidai’ (one who sacrifices his life) and its 1859 revival.
• CANDY: Nice elevator fact: the word ‘assassin’ was an enemy’s label, never the group’s own name.

Related

• The label ‘Assassin’ was imposed by enemies while the self-descriptor was fida’i (similarity 0.89)