Hat tip
A hat tip (abbreviation: h/t), also referred to as tip of the cap, is an act of tipping or (especially in British English) doffing one's hat as a cultural expression of recognition, respect, gratitude or simple salutation and acknowledgement between two persons. == Traditional == In Western societies of the 19th and early 20th centuries, a hat tip was a common non-verbal greeting between friends or acquaintances while walking or meeting at a social gathering.