The only free and comprehensive online etymological dictionary of the Spanish language
brillar (Verb) "to shine"
17th cent. Borrowed from Italian brillare 'id.' From Vulgar Latin *beryllare "to shine (like a beryl gemstone)." From Latin beryllus "beryl" (see berilo).
brisa (1) f. (Noun) breeze; "wind from the northeast," "wind from the east"
The meanings of "northeasterly" and "easterly" winds are somewhat more recent, attested as early as the 16th cent. The meaning of "breeze" dates to 14th cent. Old Spanish briza. Of uncertain origin. Compare French bise "northeasterly wind." Both probably derive from a Germanic source but a sound reconstruction is impossible.
Indo-European
Romance
Portuguese brisa, Galician brisa, French bise
Germanic
Middle English brise (English breeze), Frisian Briese "breeze," and Dutch bries 'id.'
brisa (2) f. (Noun) "residue of pressed grapes"
14th cent. From Latin brisa "refuse of trodden grapes." From an ancient language spoken in the Balkans (cf. Albanian bërsi "pomace," "lees"), argued by Pokorny (1956) to be from Illyrian *brisa "grape husks." A separate study by Orel (1998) drew roughly the same conclusion, though declining to reconstruct the word in Illyrian. From Proto-Indo-European *bher- "to be vehement," employed metaphorically by the ancients to describe the fermentation process.
Indo-European
Romance
Catalan brisa
Albanian
bërsi "pomace"
Balto-Slavic
BCS bersa "tartar," Slovene birsa 'id.'
Hellenic
Ancient Greek βρὐτεα (brytea) "pomace"
Thracian
Thracian βὐρτεα (byrtea) "pomace," βὐρτον (byrton) "beer"
The Athenians used to call pressed olives stemphyla, while brytea was their word for what we call stemphyla, being really pressed grapes. ~ Athenaeus, Deipnosophistae
briza f. (Noun) "quaking grass"
19th cent. Probably from brizo, a comparison to the steady rock of a cradle (compare Galician briza and brizo, both meaning "quaking grass").
Indo-European
Romance
Galician brezo
brizo m. (Noun) "rocking cradle"
16th cent. On the basis of its phonology, hypothesized to be from a Celtic language (several Celtic tongues were spoken in Iberia in ancient times). From Proto-Celtic *brett- or *bert- "bed," "cradle." Of unknown origin.
Variants
Old Spanish combleza "concubine," combuerça 'id.' (argued by Corominas (1987) to be from Proto-Celtic *com-bort(t)ia "bed companion," but see Spitzer (1956) for criticism)
For other possible cognates, consider brezo (2) and blezo.
broma (1) f. (Noun) "joke," "jest"
Very early 16th cent. Originally meaning "shipworm" (compare Asturian broma / groma which can mean both "jest" or "shipworm"). It came to mean something serious and destructive; later something bothersome; and finally a jest. Borrowed from Ancient Greek βρῶμα ‎(brôma) "shipworm." From Proto-Indo-European *gwerh3- "to devour."
Indo-European
Romance
Asturian broma "joke," "shipworm," Galician broma, Catalan broma "joke," "fog,"
Balto-Slavic
Old Church Slavonic žьrǫ, Lithuanian gìrtas "drunk"
Armenian
Armenian eker "he devoured," from *h1e-gwerh3-et
Indo-Iranian
Sanskrit gīrṇá- "devoured"
broma (2) f. (Noun) "dough;" "oat porridge"
19th cent. A feminine form created by folk etymology from Latin bromos "oats." Borrowed from Ancient Greek βρόμος (brómos) 'id.' Of unknown origin. Probably from a non-Indo-European language.
Indo-European
Hellenic
Ancient Greek βόρμος (bórmos) "oats"
brujería f. (Noun) witchcraft
18th cent. From bruja and the collective noun-forming suffix -ía.
Indo-European
Romance
Asturian bruxería, Portuguese Bruxaria, Galician bruxaría, Catalan bruixeria, Occitan brueissariá,
brujo (Noun) sorceror, (f.) "witch," (m.) "warlock"
Very early 15th cent. Old Spanish bruxa. Of unknown origin.

The traditional view is that brujo comes from a pre-Roman language such as Iberian or Celtiberian. If the word is a loan from a Celtic source, then compare Old Irish Brigit "bright," name of a fire goddess, whose worshippers were the brigantes. Note the old Latin name for La Coruña, Spain, was Brigantium "place of the Brigantes."

Alinei (1999) argued that the word and its Romance cognates derive from Latin bruc(h)ulus "little worm," from bruchus "grub."

Dworkin (2012) follows the work of Cazalbou, who noticed that the Old Spanish bruxa is pre-dated by Catalan bruixa, Occitan (Gascon dialect) broucho, and several Southern French forms by at least a century. In which case, perhaps the word was borrowed from a pre-Roman language spoken north of the Pyrenees.

Finally, a suggestion by Meier (1984) that brujo comes from Vulgar Latin *versiare/*vortiare has been roundly rejected by other linguists.
Indo-European
Romance
Asturian bruxu, Portuguese bruxa, Aragonese bruixa, Catalan bruixa, Occitan (Gascon) broucho, brouche, French (southern dialects) bruèis(sa), breicha, broucha
bueno (Adjective, Interjection) "good;" "well"
11th cent. From Latin bonus, from Old Latin duenos. From Proto-Italic *dwenos 'id.' Of difficult etymology, despite cognates in other Indo-European languages. There is no convincing reconstruction in Proto-Indo-European that would yield *dwe- in Proto-Italic. De Vaan (2014) tentatively hypothesizes *du̯h2-eno-, but this would become **dwano- in Proto-Italic. If the original root in Proto-Indo-European was *dh3u̯o- (from *deh3- "to give;" see dar) then a suffix *-eno- is merely an ad hoc explanation, for aside from this solitary word there is no evidence for the existence of a putative *-eno- (Mayrhofer 1992).
As a surname Bueno, originally given to those whose presence was said to be a good omen.
Indo-European
Romance
Asturian bonu, Portuguese bom, Galician bo, Catalan bo, French bon, Italian buono, Aromanian bun, Romanian bun, Sardinian bonu
Italic
Faliscan duenas "of the brave," duenom "brave"
The surprising sound shift from Old Latin du- to Latin b- is well documented: duonus "good" > bonus; duellum "war" > bellum.