What is the origin of the terms “Bourazeris” and “Vlamis”, obsolete from the 21st century Greek language?

The Triantafyllidis dictionary is online:

βλάμης [vlamis] “blood brother” < Albanian vlam: Λεξικό της κοινής νεοελληνικής. Obsolete, but certainly familiar from rebetiko and later songs. The 1951 song Παλαμάκια is probably the best known instance of the word—or rather, of its feminine vlamissa:

μπουραζέρης [burazeris], variant μπραζέρης [brazeris], was not familiar to me, and is not in Triantafyllidis. But it is in the Papyros dictionary, which is available (unattributed) online: μπουραζέρης. It is glossed as “blood brother”, and also derived from Albanian. (I recognise burrë ‘man’.)

The term occurs mostly as a surname in Google, but I found an instance of it in its literal meaning here: Ο λεοντόκαρδος και ακατάβλητος οπλαρχηγός Μ.Μπότσαρης . It mentions Theodoros Kolokotronis becoming blood brother of Markos Botsaris during the Greek War of Independence. Not coincidentally, Botsaris was ethnic Albanian (and not Arvanite: Souli is across the border from Modern Albania), and he wrote one of the earliest dictionaries of Albanian.

I note this article online: Αδελφοποιΐα – Βλάμης (Μπραζέρης)

Στην Ήπειρο, κι όχι μόνο, λέγονται βλάμηδες «από την αλβανική λέξη βλαμ» και μετά την αδελφοποίηση «οι βλάμηδες» το γιορτάζουν με φαγοπότι και χορό. Στη Μακεδονία και στη Θεσσαλία λέγονται μπράτιμοι «από βουλγαρική λέξη» και στην Πελοπόννησο μπουραζέρηδες ή μπραζέρηδες.

In Epirus and beyond, blood brothers are called vlamides, from the Albanian word vlam, and after the ritual vlamides celebrated with feasting and dancing. In Macedonia and Thessaly they are called bratimi, from a Bulgarian word, and in the Peloponnese they are called burazerides or brazerides.

EDIT: the Standard Albanian equivalents are given in Kelvin Zifla’s answer to What is the origin of the terms “Bourazeris” and “Vlamis”, obsolete from the 21st century Greek language? and in User-13249930999434776143’s comment below: vëllam, byrazer.