I am studying Middle Eastern migration to Latin America at the end of the nineteenth century. One of the popular practices among these people was peddling, and there is much research on those who sell their goods on the streets. Yet, peddler is not the only word used for them. Hawker and beggar are also used by scholars. What is the difference between these words?
Beggar is obviously different from the other two in that he is not offering goods for sale, just begging.
From the definitions, both hawkers and peddlers travel about selling things, but in my mind a hawker is more of a person who calls out their goods for sale in a public place, while a peddler may be going door to door.
As noted, beggar is quite different from the other two (so much so that it really has no place in the discussion).
A peddler and a hawker both sell things, both might use a spiel to do so, and both are itinerant. My impression of the difference is that a peddler carries his merchandise around, so his selling activities take place in varied circumstances — the marketplace in the morning, a customer's doorstep in the afternoon, the next town over by tomorrow. A hawker, on the other hand, is more likely to be associated with some sort of storefront, even if that's just a blanket in an odd corner of the flea market, and even if said blanket is in a different flea market each day of the week. There is also the possibility that a hawker is employed by the store owner, while a peddler is almost certainly working for himself.
Interestingly, my impressions are somewhat contradicted by the Online Etymology Dictionary, which under hawk (v.1) notes that
Despite the etymological connection with stooping under a burden on one's back, a hawker is technically distinguished from a peddler by use of a horse and cart or a van.
Note that whatever the differences, they're all pretty vague, and in most cases (especially modernly) peddler and hawker can be used as exact synonyms.
My (Scottish-influenced) dictionary says that the technical distinction is that a pedlar carries his goods from door to door personally, e.g. in a pack, while a hawker has a horse and cart (or possibly a van, nowadays). Peddler is the US spelling: peddle was a back-formation from pedlar or the archaic version pedder. There are no references I can check, apart from an old dialect use of ped meaning to sell; but it's plausible.