an Allegiance is a duty of fidelity said to be owed by a subject or a citizen to his/her state or sovereign.
Origin of the word
Mid. English ligeaunce; med. Latin ligeantia; the al- was probably added through confusion with another legal term, allegeance, an allegation; the French allegeance comes from the English; the word is formed from "liege," of which the derivation is given under that heading; the connection with Latin ligare, to bind, is erroneous.
Usage
The term allegiance is often used by English legal commentators in a larger sense, divided by them into natural and local, the latter applying to the deference which even a foreigner must pay to the institutions of the country in which he happens to live; but it is in its proper sense, in which it indicates national character and the subjection due to that character, that the word is important.In that sense it represents the feudal liege homage, which could be due only to one lord, while simple homage might be due to every l
Source:
http://en.wikipedia.org/wiki/Allegiance