From Latin 'insignia' (distinguishing marks) — a flag bearing an identifying mark, and the officer who carried it.
A flag or standard, especially a military or naval one; a junior commissioned officer in the U.S. Navy or Coast Guard, ranking below lieutenant junior grade.
From Old French 'enseigne' (a mark, sign, signal, standard, flag), from Latin 'insignia' (plural of 'insigne'), meaning distinguishing marks, badges of rank or office, from 'in-' (in, upon) + 'signum' (a mark, a sign, a standard). 'Signum' derives from PIE *sekw- (to follow) via the derivative sense of a marker that one follows — a signal that directs attention or movement. The same root gives
The naval rank of 'ensign' — the lowest commissioned officer grade in the U.S. Navy — originated from the practice of assigning the regiment's youngest officer to carry the flag (ensign) in battle. Carrying the colors was both an honor and an extreme danger, since the enemy targeted the standard-bearer