late 14c., "to give a title to a chapter, book, etc.," from Anglo-French entitler, Old French entiteler (Modern French intituler), from Late Latin intitulare, from in- "in" (see in- (2)) + titulus "title" (see title (n.)).
Meaning "to bestow (on a person) a rank or office" is mid-15c. Sense of "to give (someone) 'title' to an estate or property," hence to give that person a claim to possession or privilege, is mid-15c.; this now is used mostly in reference to circumstances and actions. Related: Entitled; entitling.