"fat and heavy; brave and determined"
This 14th-century word quickly developed parallel-track positive and negative meanings. One positive meaning ("brave, valiant, resolute") is heard when Richard greets some Murderers with "my hardy, stout, resolved mates!" (Richard III, I.iii.339 ). This is like the modern sense of "stout fellow!" Another ("bold, determined") is heard when King John says to the Bastard "adverse foreigners affright my towns With dreadful pomp of stout invasion" (King John, IV.ii.173). The negative senses are the most likely to mislead. The word means "proud, haughty, arrogant" when Malvolio says to himself "I will be strange, stout, in yellow stockings and cross-gartered" (Twelfth Night, II.v.164),Volumnia describes her son as having a "stout heart" (Coriolanus, III.ii.78), or Salibury describes the Cardinal as "stout and proud" (Henry VI Part 2, I.i.185). There is no sense of "fatness" here. That sense did not arrive until the 19th century.
David Crystal is author, with Ben Crystal, of Shakespeare's Words, published by Penguin