It’s so named because it’s the 7th from a major scale, and not the more usual flattened variety, associated with the blues.

Napoleon’s achievement was on a vast, world-transforming scale, and Beethoven’s symphony has a similar ambition. To me the ‘Eroica’ chord expresses a sense of fighting free from oppression ...

chords are numbered, to show the position of the note relative to its scale. Chords are numbered in Roman numerals. For example, in the scale of C major, the chords are numbered like this ...