Language: Nias
Source: Period accounts
Description
Belatu is a generic word for "knife" or "sword" in the Nias language.1

A sword from Nias.
Mandarin Mansion stock 2020.
Today it is used by collectors to refer to any knife or sword from Nias, but according to Schröder, who worked on the island as a colonial administrator from 1904 to 1909, this was wrong and the locals referred to the different types with different names entirely.
Types of knife / sword according to Schröder
His descriptions are a bit cryptic, but I will repeat them nonetheless. These are my direct translations from the orginal Dutch.
1. Bulu sewà (north) / balatu salà (south)
The edge is shorter than the spine and there is a bend in the transition.
(Possibly Fischer type B. See below.)
2. Tòmbà (north) / telögu (south)
The edge is much longer than the spine and transitions sharply into the spine.
(Fischer type C. See below.)
3. Gari or gari matuwà
The edge is considerably shorter than the spine. There is first a sharp bend and then a gradual transition to the point. There are two subtypies, one with a straight spine and another with a curved spine. The latter is also called sò bawa wötō, with a point like the beak of a woodpecker.
(Possibly Fischer type A. See below.)
4. Ròsō (north) / sirawi (south) / ono balatu (elsewhere)
Daggers of different sizes.
5. Rudu
A small curved saber of which the edge is longer than the spine.
6. Balatu (sebuwa) (north) / belawa (gari) (south)
A crude bulu sewà, the working knife used in the fields. Many different varieties exist.
Fischer typology
Fischer, writing in 1909, presents a typology of both hilts and blade shapes. He uses numbers for each type and does not provide native names for each.2

Belatu blade types. Drawing by author, after on illustration in Fischer.
The edge is emphasized for clarity.

Belatu hilt types. Reproduction of the illustration in Fischer.
A glossary of terms
Schröder names a great deal of terms relating to Nias knives and swords in his work.3 I made a visual overview below.

# |
English |
North Nias |
South Nias |
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1 |
Hilt |
dànga |
dràga |
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2 |
Brass ferrule |
sàngò |
siànò |
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3 |
Animal pommel |
niòbawa lawölò |
niòbawa lawölò |
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4 |
Monkey figure |
bekhu |
bekhu |
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5 |
Back of blade |
tu'i |
tu'i |
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6 |
Edge of blade |
bawà |
bawà |
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7 |
Ricasso |
böna |
böna |
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8 |
Transition to edge |
fusō |
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9 |
Middle edge |
dalu |
talu |
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10 |
Point |
ighu |
ighu |
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11 |
Scabbard |
sàèmbu |
sàèbu |
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12 |
Scabbard bands |
làojo nifali |
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13 |
Scabbard mouth |
telàu dsèbu balatu |
Production
Steel was imported into the island from China by Chinese merchants and worked locally into blades. Hilts are usually made of wood, but sometimes ivory or buffalo horn was used, which was imported from nearby Sumatra.4 In rare instances, gold was used, this came primarily from slave trade with North Sumatra.
Notes
1. Engelbertus Eliza Willem Gerards Schröder; Nias. Ethnographische, geographische en historische aanteekeningen en studiën. Brill, Leiden. 1917. Page 235.
2. Fischer, H.W.; Catalogus van 's Rijks Ethnographisch Museum, Deel IV, de Eilanden om Sumatra. E.J. Brill, Leiden, 1909. Page 39.
3. Schröder. Pages 236-239.
4. Th. C. Rappart; Het Eiland Nias en Zijne Bewoners. Bijdragen tot de taal-, land- en volkenkunde. s' Gravenhage. 1909. Page 529.