"not large in size or amount"
The modern meaning of the adjective is over 1,000 years old, and is common enough in Shakespeare, where we find "small curs", "small thanks", and many other "little" things. But we sense a different meaning when we hear Gower describe Marina's fingers as "long, small, white as milk" (Pericles, IV.Chorus.22). How can fingers be both long and small? Here, the word means "slender" or "slim". We see it again when Launce describes his sister as being "as small as a wand" (Two Gentlemen of Verona, II.iii.20). Another meaning is "fluting" or "high-pitched", as when Slender describes Anne as someone who "speaks small like a woman" (Merry Wives of Windsor, I.i.45).
And there is a third meaning, "weak" or "poor", heard when Edward describes a city as being "of small defence" (Henry VI Part 3, V.i.64) - a sense that also enters into the idioms small beer and small ale.
David Crystal is author, with Ben Crystal, of Shakespeare's Words published by Penguin