Beard: from chin to metal edge
Most people grow facial hair; printers inherit a metal edge from the days of movable type.
To everyone else, a beard is facial hair, the stubble or whiskers that grow from a man's chin and cheeks. It is ordinary, visible, grown from skin. In a print shop or type foundry, a beard is something entirely different: a narrow band of metal that sits on a metal letter.
When type was cast by hand, each piece of metal type consisted of a shank, the thick rectangular stem that held the letter, and a face, the raised surface that would be inked and pressed onto paper. Between them lay the shoulder. The beard is the small vertical strip of metal that runs between the shoulder and the face, on the sides of the letter. It serves no printing function and carries no impression. It is simply there because of how the letter was cast in its mold.
The beard matters to the printer because it affects spacing and fit. Too much beard, and letters crowd together or sit unevenly in the composing stick. Too little, and the type is weak. The beard also helps protect the delicate face of the letter from damage during handling and storage. For centuries, until phototypesetting made this craft obsolete, understanding the beard was part of a printer's craft knowledge.
The word itself is likely metaphorical: just as a beard frames the face on a human head, the beard on type frames the face of the letter. Both are secondary to what matters most, yet both are inevitable features of the form. The term appears in foundry records and printer's manuals from at least the 18th century, embedded in a technical vocabulary that treated metal type as a precise, engineered object.
The dictionary entry
beard
(noun, industrial printing)
That part of a type which is between the shoulder of the shank and the face.