One theory says this practice came from knights lifting their visors when greeting a friend
The most 
widely accepted theory is that it evolved from the practice of men raising their 
hats in ... Perhaps the courtesy of a knight raising his helmet's visor on... [DOC] [TLE] Free Flashcards about MIDDLE AGES - StudyStack [PAR] ONE THEORY SAYS THIS PRACTICE CAME FROM KNIGHTS LIFTING UP 
THEIR VISORS WHEN GREETING A FRIEND, SALUTING.