The Sardinian onomastic system is very different from the Italian one, nearly all Italian surnames end with I, while 90% of Sardinian surnames end with U (since they are in Sardinian language and not in Italian), many others instead end with S, (Sardinian has plurals with S). Our surnames derive from ancient nicknames about physical features, jobs, place names etc.etc.
(You can usually recognise a Sardinian from his surname, very different from those of the continent.)
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Arcadu = literally "arched" = bent, awkward
Bassu = short
Bonu = good
Brundu = blond
Canu = white haired (Latin "canus")
Concas = heads
Corrìa, Corrìas = leather lace/laces
Cossu = Corsican
Crastu = boulder, rock (Latin "castrum")
Cuccu = cuckoo
Deriu, De Riu = of the river
Dessena = contraction of "de sa 'ena" = of the source/vein
Falchi (Italianized) - Falche (correct Sardinian pronunciation) = scythe
Ladu = wide (Latin "latus")
Lòriga = iron ring, chain ring (Latin "lorica" = mail with iron scales)
Manca = left, left handed
Mannoni (Italianized) Mannone (correct Sardinian pronunciation) = beef
Mannu = big (Latin "magnus")
Marras = incisive teeth (plural of Latin/Sardinian "marra" = hoe)
Melas, Demelas = apples, of the apples
Nieddu = black (Latin "nigellus" = blackish)
Piga = magpie (Latin "pica")
Pinna = pen, fin, nostril
Piras = pears
Porcu = pork
Porcheddu = little pork
Puddu = chicken
Rassu = fat
Russu = large
Ruju = red
Santoru = of the saints (Latin "sanctorum")
Sedda = saddle
Seddaiu = saddle maker
Serra = saw
Tanca = enclosed plot of land (from verb "tancare" = to enclose