In referencing Webster's dictionary of 1828 I came across the entry for the word 'Han'. The definition was stated as: "for have, in the plural." Source: Spenser. What does this mean and how was it used way back then?
At one point, a common conjugation of to have was:
Now I say "a common conjugation" because there were plenty of variations, and you might find someone using "we have" while still using "they han", or "we han" with "they hast" or "they have", and so on.
So as you can see, han was used "for have, in the plural" as that dictionary says.
Now we would use "we have" and "they have".
I imagine the use was already mainly historical by 1828, but maybe a dialect use remained.
Webster's main conjugation is:
I have, thou hast, he has; we / ye / they have
Which would suggest that han was no longer current in most dialects at least, but of course people might still come across it (reading Spenser, perhaps…) and look it up.
For an example of how it was used, let us indeed take a look at Spenser. Compare this excerpt from "The Shepheardes Calender":
For shepeheards, sayd he, there doen leade,
As lordes done other where;
Theyr sheepe han crustes, and they the bread;
The chippes, and they the chere:
They han the fleece, and eke the flesh;
(O seely sheepe the while!)
The corne is theyrs, let other thresh,
Their hands they may not file.
They han great stores and thriftye stockes,
Great freendes and feeble foes:
What neede hem caren for their flocks?
Theyr boyes can looke to those.
...with this slightly modernised version, "The Shepherd's Calendar":
For shepherds (said he) there do lead
As lords do otherwhere;
Their sheep have crusts, and they the bread;
The chips, and they the cheer:
The have the fleece, and eke the flesh
(O seely sheep the while!)
The corn is theirs, let others thresh,
Their hands they may not file
They have great store and thrifty stocks,
Great friends and feeble foes;
What need they caren for their flocks,
Their boys can look to those.