Monogram

A monogram is a motif made by overlapping or combining two or more letters or other graphemes to form one symbol. Monograms are often made by combining the initials of an individual or a company, used as recognizable symbols or logos. A series of uncombined initials is properly referred to as a cypher (e.g. a royal cypher) and is not a monogram.

Monograms first appeared on coins, as early as 350BC. The earliest known examples are of the names of Greek cities who issued the coins, often the first two letters of the city's name. For example, the monogram of Achaea consisted of the letters alpha (Α) and chi (Χ) joined together.

Monograms have been used as signatures by artists and craftsmen on paintings, sculptures and pieces of furniture, especially when guilds enforced measures against unauthorized participation in the trade. A famous example of a monogram serving as an artist's signature is the "AD" used by Albrecht Dürer.

Over the centuries, monograms of the name of Jesus Christ have been used as Christian symbols. The IX monogram consists of the initial Greek letters of the name "Jesus Christ," "I" for Ιησούς, (Jesus in Greek) and "X" for Χριστος (Christ in Greek). The "IHS" Christogram, denoting the first three letters of the Greek name of Jesus, is usually written as a cypher, but sometimes as a monogram. Perhaps the most significant Christogram is the Chi Rho, formed from the first two letters of Χριστος.

Signum manus (sometimes also known as Chrismon) refers to the medieval practice, current from the Merovingian period until the 14th century in the Frankish Empire and its successors, of signing a document or charter with a special type of monogram or royal cypher.

...
Wikipedia