The OP seems to confuse heavy infantry/cavalry with elite; thus, here's one definition of the word "elite" (especially during EB's timeframe, 2. & 3. would've been the most accurate definitions):

e⋅lite
  [i-leet, ey-leet]

–noun
1. (often used with a plural verb) the choice or best of anything considered collectively, as of a group or class of persons.
2. (used with a plural verb) persons of the highest class: Only the elite were there.
3. a group of persons exercising the major share of authority or influence within a larger group: the power elite of a major political party.
4. a type, approximately 10-point in printing-type size, widely used in typewriters and having 12 characters to the inch. Compare pica 1 .
–adjective
5. representing the most choice or select; best: an elite group of authors.
Also, é⋅lite.

Origin:
1350–1400; ME elit a person elected to office < MF e(s)lit ptp. of e(s)lire to choose