From the archives:

Biceps comes from the Latin words bis (twice) and caput (head). The biceps brachii is a muscle with two "heads" (or origins).

"Biceps" is typically used in both the singular and plural, though to be strictly proper the correct plural form is "bicipites". About a quarter of the usage on the Internet is the incorrect, pseudo-singular "bicep".

The biceps brachii was named in 1734 by the German anatomist Bernhard Weiss (who went by the Latinized name of Albinus).

Albinus (1697-1770) commons.wikimedia.org